New Hopefuls - Army Reservist Michael Gallant and brash Gregory Pratt - arrive to face the challenges of Trauma One life. A familiar face - Dr. Susan Lewis - returns. Benton weighs career and family. Malucci crosses the line once too often. Chen defies demotion. And Greene fights what could be his last battle, leaving a void at the group's heart. His leadership may never be replaced. But someone must step into the breach. That someone is the doctor who's now been in the ER the longest - the former student who seemed to have the most to learn: Dr. John Carter.