So, Jason and Medea were married and had two kids together and were fine at first. Then Jason kinda just went behind Medea's back to wed the princess of Corinth (the land they're living in) with king Kreon's blessing.
As you might also share in thought,
Medea is all, >8{ "Dude, what the f*ck?! You bastard! We're married, and we got kids! You lying son of a b*tch!"

but she's also like, QAQ "Great! Well, I guess our love was a f*cking lie, and I've been totally used like a disposable bag! I hate looking at my kids because they remind me of Jason, and I hate Jason for totally doing this bullshit to me, and I just wanna die! I can't live with this horrible grief!"

Meanwhile everyone in Medea's house is like concerned for her because they know she's like some weird foreign priestess and is super clever and might be cooking up a wicked or evil scheme in her anger and woe.
And she knows Jason is having fun with his new wife because he doesn't even visit her or the children often.
The house nurse tries to console her and keep her calm but Medea is all, ;n; "What good is it to keep on living when I've totally been betrayed and now everyone is talking about me? Leave me the hell alone and go play with the kids or whatever..."
Then king Kreon comes for a visit but it's not a very cool visit at all.

He's like, >:/ "Medea, you gotta go. You gotta just take your kids and just get the hell out of my kingdom."
And she's like, Q-Q "What?? Why? What did I do?"
And he's all, >:/ "Well, you're kinda creeping me out. I don't want some spooky witchcraft or curse to come to me because you're pissed off Jason is marrying my daughter. So, yeah, you need to leave my kingdom before you get mad and try to kill me or my daughter. So leave. Like now."
And Medea is like, QnQ "I don't have any place to go. My own kingdom hates me, and I have made enemies with Iolcos 'cause I convinced the princesses that their dad could reverse his ailing health if they, like, chopped him up and put plants on him. But really I did all that sh*t for Jason, so he could rule but they got mad, and this kingdom was the only place we could go."
And king Kreon was like, >:[ "Not my problem."
So Medea was like, Q~Q "Oh please Mr. King! I'm just a sad, poor, heartbroken lady! Just give me a day to leave then so I can figure out where I could go live in exile! So much sh*t has been going on and I feel really bad right now."
And he was like, >:/ "Hmm...I'm not totally mean. But I might regret this later. Ok. I'll give you one day, but if you're still in my land come tomorrow morning, I'm going to order to have you killed, okay?"
So Medea was like, QuQ "Ok. Thank you Mr. King sir."
but then goes back to crying her eyes out because now she's got a day left to live, no one to accept her exile and the thought of having to bring her kids which would mock her memory of Jason for the rest of her life.

And as Medea is lamenting over this huge bummer, Jason shows up!
And he's all like, :( "Hey Medea. Just visiting to tell you that you're making way too much of a fuss over this. And also to let you know that I told the king to let you stay, but he decides what he decides I guess. I know you're upset, but I still like you too, y'know? I don't wanna see you killed."
And Medea totally explodes like, >D< "Oh! Shut! Up! YOU'RE the cause of all this! Don't you DARE tell ME I should be okay with ANY of this! If anything I should be MORE upset that you're even showing your FACE here! I did everything for you! I saved you from hell-bulls, I saved you from the dragon guarding the fleece, I saved you from my own brother and father, and I left my home behind for you, AND I help kill your uncle for you so he wouldn't come after you! And THIS is the thanks I get for everything I did for YOU?!"
And then Jason is like, B[ "Look. Thanks for all that, but you don't understand. It's not every day a guy gets an opportunity to marry a princess and get a whole bunch of money, influence and economic status in one wedding day! I saw an open door and I walked through. Now I don't have to worry about anything anymore. That's totally why I married, see? Not for love, but so I can give us a nice life together."
And Medea is like, QnQ "Woah, really?"
And Jason is all, :) "Sure. It was easy. Plus, I can have more kids with the princess and all of our family can live as brothers in comfort and luxury. Isn't that an awesome plan?"
And after hearing that Medea was like, T~T "You are a god-damned piece of garbage."
Then Jason goes like, <:C "Aww come on, don't be like that. You women always think with your hearts instead of your brains. Just say you'll stop making a fuss and agree. We'll be so happy, you'll see, if you change your mind about all this. Here, I'll give you some money to help find a place in exile, just so you aren't totally helpless."
And Medea is like, >8( "No f*cking WAY! I'm not taking ANYTHING from YOU! Why don't you just go home to your new whore wife and choke?!"
And Jason was like, :/ "Well okay! I tried to help you, remember that! I'm not a bad dude for offering help! But you're a bad dude for refusing it."
And Medea goes, >8C "SHUT UP AND GET OUT!"
And so he does.
Leaving Medea to her seething emotions and bitterness.

Then outta nowhere another king shows up. xD
King Aigues from the kingdom of Athens. He's an old friend of Medea's.
He sees her and is all like, :) "Oh, hi Medea! Haven't seen you in a while!"
And Medea goes, :( "Hey Aigues. Welcome. How goes it?"
And he says, ^_^ "Ah, well I just came from the Oracle around here to see what the gods can do about me and my wife. We're trying to have kids."
And Medea was like, 8( "Holy sh*t, STILL? You don't have kids yet?"
And he's like, <:c "No. No luck at all."
And Medea goes, :( "What did the Oracle say? Tell me. Maybe I can interpret the message."
But king Aigues says, :) "I'm sure you could, but I'm gonna go discuss it with Pittheus. He's like, a way smarter king than I am."
So Medea goes, <B( "Oh, yeah you're right. Ok...good luck with that."
Finally king Aigues catches on and sees her all sad n' stuff.
And he says, <:c "Hey, you ok? What's wrong? You look like you just suffered a huge bummer or something."
And Medea spills the whole ordeal to him like, QnQ "And now I don't have anywhere to go. I'mma die, my kids are gonna die. I already feel dead and it's all my fault for trusting frickin' Jason!"
But Aigues goes, <:) "Well, hey, no worries. I'll let you stay in my kingdom secretly. I'll keep you safe. You're my friend, but no one can know that, I got a reputation to uphold you know? So make sure you come to Athens by yourself and if you can make it there, I'll keep you totally protected."
And Medea goes, ;u; "And with my remedies and drugs I'll help you with your conception issues. Okay! I'll go to Athens, but you gotta swear an oath that you'll take me in and defend my life no matter what, okay?"
So king Aigues goes, /:) "That's a little intense of you but, ok! I swear. See you later!"
And Medea goes, /;U;\ "Thank you so so SO much! 'Kay bye! See you later tomorrow!"
And he goes on his way.

Medea then comes up with a brilliantly wicked and crazy ass plan.
She goes, >:] "Now that I have a place to safely stay, I'm going to wreck the hell outta this kingdom and make Jason PAY!
I'll get one of my servants to call Jason back here and get him to believe that I want a truce and I'm okay with his idea after all. Then as a token of good will, I'll send the children with him to look after in the hopes that he'll let them stay with him and won't have to be exiled along with me. But they'll present proof with a gift to the princess. I'm going to gift her a dress so fine and lovely, with a golden crown so shiny, and she'll never suspect I dipped them both in the most vile of poisons! THEN, I'm going to have to kill the kids."
She sort of struggles with this part of the plan, because as much as they are Jason's kids they are also hers.
So she's like, <x( "I have to kill them. Not just to hurt Jason, but so if anyone comes after me sent by the king, they won't be killed by enemies. It's much better if I know they were safely done away with by my hand, than to bear the pain that they might be killed by any other hand. Oh, but I'll miss them so much! And I'm going to really hate myself for it! And I won't ever get to see them grow up. But I don't want them to suffer like me...Ok. It's settled. They die too."
And the chorus, (which is like the music vocals of reason and semi-narration, semi-poetry outside the play that hardly interacts) tells her, :( "Wow, yeah, Medea, maybe that isn't such a good idea. You're totally in the right, but don't kill your kids. That's crazy."
But Medea is like >:( "Shuddup. You can't tell me what to do."
And then she sends her nurse to fetch Jason.

So Jason comes back with the nurse and his attendants and is like,
/:( "Well, what is this now? What do you want?"
And Medea puts on a whole show like, QUQ "Oh Jason! I was wrong! Please forgive me! I didn't mean any of the sh*t I said to you, I was just being super emotional! You know how us women get. We're stupid because we're ruled by our hearts, see? I want there to be peace between us now. Do you think you could get the king to keep the kids safely here, while I leave? I think it's best they have the lives they deserve here with you and your bride."
And he's like, :/ "Oof, I don't know if I could convince him, but I'll try since you want peace after all."
And Medea's like, ;U; "Why don't you ask the princess if she could put in a good word for them, then?"
And Jason's like, :D "Oh, hey totally, yeah! I can convince the king with the princess' help!"
So Medea goes, <x) "Fan-f*ckin'-tastic! Here's the kids and they have a gift for the princess, from me! Make sure that she gets the dress and crown, okay kids?"
And she ushers the kids to Jason.
Jason goes, /:) "Ohh, she doesn't need any more dresses or gold, we got plenty of that sh*t back at the palace."
But Medea goes, ;U; "Oh, but Jason, all ladies love gifts, and even the gods love them! You'll see she'll be so happy when you come back with something pretty for her! I know I would!"
And Jason accepts the kids with the gift and goes off back to the palace, like, :) "Ok. Thanks Medea! I'm glad you're not upset about all this anymore! Have a nice exile!"

And Medea just waits while her plan works itself out.
Finally one of the servants, the kid's tutor, comes back to tell Medea that the kids delivered the gift to the royals but they were sent back so no safety of exile for them. At this, Medea breaks down in woe because she had a feeling the king didn't want her kids there and now, she has to kill them after all. She calls over her kids and gives them affection and weeps in woe for them, because she knows she won't ever see them again after her murderous deed. But she kinda wants to know if part 1 of her plan had worked and that the princess is dead, so she goes to the palace.

Near the palace, she encounters one of Jason's servants, a messenger, who is running away in terror and seems really shooken up.
So Medea is like, :O "Ey! Tell me what happened!"
And the messenger is like, 8( "Holy sh*t! Medea! You gotta go, we gotta leave ASAP! You gotta go NOW!"
And she's like, /:( "Okay, but, tell me what happened!"
And he's like, 8C "The Princess and King are f*ckin' DEAD man! Also some of the servants who touched her and her dress!"
And Medea goes, >:D "YES! Awesome! You're my helper now, you work for me."
And messenger is panicking like, /8( "What?! No! What the hell? Why are you happy about this?! The entire house of the king is so f*cking pissed off! We gotta go."
And Medea is like, Bp "We're not going anywhere until you spill the juicy details. Tell me everything! Please tell me exactly how it all happened! I gotta know for sure."
So the messenger goes, 8c "Well, your kids came in with Jason and the princess didn't seem to like them, but Jason convinced her to accept their gift and she really liked it. Everything was cool at first, when she tried it on and put on the crown. She looked so fair and pretty. But then after a bit, she started to weaken and change color, and then a servant tried to help her, but she started like, foaming out the mouth, and she f*ckin' caught FIRE, and her skin started to melt off with the dress and her hair and face were burnt beyond recognition! Like, blood and fire was oozin' out her head it was horrifying! The servants that touched her died too, so we kept away from the corpse, but the king didn't know, and he mourned ontop of her, wishing he was dead too. His skin started to rip and burn too and he couldn't get up from the toxin's hold, and he slowly died with her. So I guess he got his wish pretty quick. But anyway, I'm outta here! Wealth and fortune might be great but happiness is a lie!"
And the messenger leaves quickly.
Medea, satisfied with part 1 of the plan, now dreads completing part 2, which is the whole child-killing part, but she's like,
;~; "I gotta be brave. And I gotta do it quick. I have to pretend they aren't my kids for today. I'll mourn later, but they gotta go."
So she goes back to her house and takes up a blade.

The kids are heard screaming as they die offstage like, QCQ "Oh my god help us! She's killing us! There's no escape! F*ck! We're doomed!"

And then Jason arrives shortly after.
He's like, >:( "Where is Medea? She's gonna pay for killing the princess and the king yo! I know she did it! She can't hide. She's gonna die for this and she deserves it, but I know they'll wanna kill the kids too, so I came to save them from punishment and stuff!"
And the chorus tells Jason, :( "Oh my god, Jason, she just killed the kids."
And Jason is like, 8( "What?! NO, not my kids!"
And he sends his men to help bust down the gate to Medea's home but she shows up in a chariot drawn by frickin' dragons, and has her kid's corpses with her.
And she's like, B( "That's right motherf*cker, I killed the kids. And you can't touch me now. I got frickin' dragons with me here."
And Jason weeps in agony, goin' >:'{ "You psycho, you killed the kids! You left me childless! No way any human woman would kill their own kids! You're an evil monster! You ruined my whole life now you psychotic b*tch! There's nothing now, my life is over! You took it all! Are you happy now?!"
And Medea is like, B) "Yep. And it's all your fault. You brought this on yourself, when you betrayed me and forsook me and our sons. Now we both have to pay for it. See? 'Cause the kids are dead? Look at them, they're dead."
And Jason was like, ;A; "That's not fair! I'm in so much pain! You took them away! Poor kids. Your mom is such a monster. I loved you so much."
And Medea is like, >8( "LIES! I loved them! YOU didn't even KNOW them!"
And Jason goes, >8'( "Give them to me, so I can bury them properly!"
And she's like, B( "No, I don't think so f*cker. They're coming with me. I'll bury them with in a safe land and leave you as cold and sh*tty as you made me feel. Go home and bury your melting slime of a wife."
And Jason says, ;~; "Fine! I'll go! But just so you know, I wish I never married and had kids with you!"