David Lengel

House and the team treat a high-profile fitness trainer who collapses while shooting an infomercial; Thirteen participates in a clinical trial led by Foreman.

A famous comic-book artist (guest star Frankie Muniz) helps to search for a serial killer in Los Angeles.

Charlotte faces painful memories of a horrible tragedy; Amelia continues to spin out of control; Addison takes a step closer to motherhood.

Kate visits Toby.