John Prosky

Izzie seems to be getting over Alex when she shares an undeniable chemistry with Denny Duquette, a patient who's awaiting a heart transplant, and George treats Bex, a young teen hermaphrodite.

Peggy is faced with Leviathan's fury as she tries to save Howard Stark -- and the world.

Emily learns the identity of a key conspirator against her father; Victoria sets a trap for Emily.

Are there zombies among us? Megan is joined by the new health commissioner in her quest to uncover the truth.

A body is found covered in scratches, leading the BAU to believe that the person responsible has a chronic skin disorder.

Dr. House shows special interest in a schizophrenic with deep-vein thrombosis and her teenage son, who is her primary caregiver.