"We docked at Starbase 133 for scheduled crew rotation. I welcomed aboard my mentor and dear friend, Dr. Dalen Quaice, who is traveling with us to his home planet, Kenda II. He chose to retire after the death of his wife, which reminded me of my own sense of loss after the death of my husband Jack. Now Dalen is missing, and there is no record of him coming aboard."
Wesley and Geordi are involved with an experiment in engineering as the Enterprise takes on new crew members at Starbase 133. Dr. Crusher welcomes on board an old friend, Dr. Dalen Quaice who seemingly disappears overnight without a trace. In fact, no one, including O'Brien who beamed him up, remembers seeing him and there is no trace of his existence anywhere in Starfleet. As the crew begins to vanish, also without a trace, Dr. Crusher struggles to convince Picard that something is wrong and comes to doubt her own sanity.