On Thursday's all-new episode of Grey's Anatomy, "Desire," the attendings vie to be Chief. Not surprising, we know.

But here's one that you might not see coming - two characters who haven't slept together before will do so. Dr. McSteamy's 60-day vow of chastity, meanwhile, comes to its conclusion.

Elsewhere, we're introduced to a boss, his assistant, and his wife. We also get to see someone being treated in the clinic, and Derek (surprise) has more questions about his relationship with Meredith.

Here's a preview...

[youtube]http://www.youtube.com/watch?v=HeaRskaOKGY[/youtube]

Here's an extended clip from the episode...

[youtube]http://www.youtube.com/watch?v=eUFHbagU9xo[/youtube]

As usual, we'll have our episode recap, music guide, image gallery and list of quotes up after the show. Follow these links to our thorough recap from last week's "Time After Time," as well as its music, pictures and quotes.

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.