Seven's implant fails and Icheb risks his life.
After three of the former Borg children leave Voyager with their own people, Seven of Nine finds herself in tears, which she blames on a faulty implant. Soon her cortical node, a key Borg implant, fails, and without it she will die. A replacement taken from a long-dead drone in a Borg debris field proves too old to work, and Seven accepts that she may not survive.
Icheb, who wants to sit the Starfleet Academy entrance exam, offers his own node, since he was never fully assimilated and can live without it. When Seven refuses, he sets his alcove to shut his node down and force the issue. The crew finally agree, and the transplant succeeds. Seven tells Icheb that his act was foolish, then thanks him and promises to help him study. The seventh-season opener is a story about family and sacrifice, and it ends with Seven crying again, this time because she feels love.