is the 14th episode of the fourth season of the medical drama Grey's Anatomy , which originally aired on May 8, 2008. Primary Plotlines

: The episode features a tribute to military members, centered around the veteran patient and his partner. "Grey's Anatomy" The Becoming (TV Episode 2008) - IMDb

: Meredith Grey and Derek Shepherd admit a military veteran into their clinical trial. They work on synchronizing their virus injections into a tumor during a simulation.

: Izzie Stevens discovers that Ava is not actually pregnant and is experiencing a psychological break, but she struggles with maintaining patient confidentiality versus telling Alex.

: Callie Torres and Erica Hahn share an awkward but improving dynamic at Joe's bar after Addison Montgomery's previous comments about them.

: Meredith's therapist, Dr. Wyatt, challenges her on her "cowardice" regarding her fear of a relationship with Derek, leading to a tense confrontation. Notable Scenes & Details

: Richard Webber appoints George O'Malley to manage the new dating forms to prove he is delegating effectively to his wife, Adele.

: Following complaints about Mark Sloan's multiple trysts, the nurses go on strike against him. This leads to the implementation of a "date-and-tell" policy at Seattle Grace, requiring all staff to report sexual relations.