In season 3, Cristina Yang (Sandra Oh) and Burke (Isaiah Washington) were engaged.
They were working together.
They were in love.

Credit: ABC
Then Burke left Yang at the altar, and that was the last we saw of him.
But what will happen between the two?
But if we’ve learned anything fromGrey’s, it’s that timing can be everything.
But now look at them, using Post-its for things other than grocery lists and having babies!
Cristina wasn’t ready to get married then, and Burke knew that.
And then he left.
Since then though, Cristina’s been married and divorced.
Not gonna happen.
Not only do they have a history, but he is oh-so-romantic.
Dump Yang, and marry me."
Who doesn’t want that?
Burke dies, Version 1
Grey’sloves killing off our favoritesrest in peace, 007.
Cristina turns out to be his doctor, and she finds the old feelings she had for him return.
Sure, he’s on his deathbed, but this is true love.
Burke’s all she wanted all along, she just wasn’t ready for marriage when he was.
This is one of these oh-my-god-I-messed-up epiphany moments, and then Burke dieshe dramatically codesand he’s gone forever.
“I’m free!”
she cries as she leaves.
(Too much?)
She’s done with holding onto memories formed in the hospital.
Cristina is having doubtsis Owen worth leaving her best bud Meredith for?
Is it actually going to work this time?
Then she finds out Burke is visiting the hospital to showcase this great new procedure he invented.
Cristina has a bunch of emotions because, duh.
Some of these emotions are “What if I’m still in love with him?”
emotions, which just add to all Cristina’s fears about settling down with Owen.
Burke shows up, and Cristina feels nothing.
He’s all, “I made a mistake!”
Later in the episode, Cristina is finalizing plans to move in with Owen.
Still loopy, Yang has a one-sided heart-to-heart with him and is uncharacteristically mushy.
Her condition worsens and she passes out so they rush her into the OR.
He gave her life, and now she needs to live it.
This means leaving Seattle and pursuing her dream heart surgeon job somewhere far, far away.