“Games People Play” is episode four of season two of Eureka.
Carter’s ex-wife is still in Eureka, and is still planning to take Zoe back to LA as they agreed. Zoe is not exactly happy about this. Henry, meanwhile, has discovered that Beverley is lying about how she interacted with Kim.
Carter and Jo get called out to a noise complaint. The scientist in question is conducting an experiment to identify both the location and momentum of an electron at the same time. Which does sound like it has potential problems, if successful.
Afterwards, back at the office, Carter is talking to Jo, although she’s in another room, when she vanishes. When he asks around, no-one else remembers her. More people keep disappearing, and Carter is the only person who remembers they ever existed.
This reminded me quite strongly of a Star Trek: The Next Generation episode.