Plumbing leak becomes a deluge and wreaks havoc at Seattle Grace, as the Chief attempts to implement new teaching policies and George tries to retake his residency exam; meanwhile Derek hopes to move the roommates out of Meredith's house, to their surprise.

Bailey heads up a team of surgeons performing a "domino procedure" in which each surgery hinges on the one preceding it; Derek gets sole credit for the brain tumor study he did with Meredith; Lexie goes to great lengths to have George notice her romantically, and Sloan counsels a desperate Callie on the ways of love.