Rescued from a near-fatal encounter with the Wraith, Lt. Aiden Ford (Rainbow Sun Francks) receives medical care at the Atlantis base. However, his abnormally quick recovery leads Dr. Beckett (Paul McGillion) to worry that the Wraith who attacked Ford may have injected him with a harmful enzyme, causing long-term and unpredictable damage. Meanwhile, as the Wraith’s siege of Atlantis rages on, Sheppard (Joe Flanigan) finds himself surrounded by the enemy. He is rescued by the timely arrival of Colonel Steven Caldwell (Mitch Pileggi), commander of the Daedalus. Launched from Earth and sent in to assist the Atlantis team during battle, the Daedalus helps to defeat the Wraith’s first wave assault on the city. Their relief is short-lived, however. The team soon learns that the Wraith are planning the next wave of their onslaught -- an entire fleet is about to descend on the city. With a little over a day before the assault, Dr. Weir (Torri Higginson) realizes that the Daedalus will not be enough to fight the Wraith's forces. McKay (David Hewlett) devises a drastic plan - but there may not be enough time to perfect the complicated technology his plan requires before the Wraith arrive.