The Doctor discovers that his short-term memory has been altered with some events being deleted, so he launches an investigation into whom or what could be responsible. When he sets a trap and the culprit is caught, he is shocked at who it is and why they're doing it.
Elenco: Kate Mulgrew , Robert Beltran , Roxann Dawson , Robert Duncan McNeill , Ethan Phillips , Robert Picardo , Tim Russ , Garrett Wang , Majel Barrett , Jeri Ryan .