On the first day back from her honeymoon with Cristina, Meredith comes face to face with a half-sister she never knew existed, who has joined the group of first year interns at Seattle Grace. On top of that her half-sister is the "the girl from the bar" that Derek was referring to. With Meredith's emotional withdrawal from their relationship could Lexie Grey be the next intern to sleep with an attending?

Lexie Grey desperately wants to get to know her step-sister Meredith when she arrives for her first week as an intern, but finds she's met with an icy-cold resistance - much like the experience Derek has been faced with.

Will the two people who want so much from Meredith end up turning towards each other to find what has been missing all along? Will Meredith push the very person who loves her the most towards the person she loathes the most, the daughter her father did love?

Let us know what you think will happen between Derek and Meredith in Season Four of Grey's Anatomy.