S4, E15: In the first part of a two-part season finale, House finds himself dazed, confused and covered in blood after surviving a bus accident that left dozens seriously injured. Unable to clearly recall the events leading up to the crash due to his head injuries, House becomes convinced through his flashbacks that a fellow bus passenger was exhibiting signs of a deadly illness prior to the crash. Much to the team's dismay, House pushes through the pain of his own injuries, desperate to piece together the fragments of his shattered memory in order to save someone who might not even know he or she could be dying in the "House's Head" episode of House. Viewer discretion is advised.