GREY'S ANATOMY - "Valentine's Day Massacre" -- It's Valentine's Day, and the doctors must treat dozens of injured people after the roof collapses at a popular romantic restaurant; Derek tries to manage his busy schedule as Chief of Surgery; Meredith wrestles with her new duties as the Chief's wife; and Mark and Callie team up to convince Sloan to do the right thing for her baby, on "Grey's Anatomy," THURSDAY, FEBRUARY 11 (9:00-10:01 p.m., ET) on the ABC Television Network. (ABC/DANNY FELD) ELLEN POMPEO