Randall and Hopkirk (Deceased) (1969)

Season 1: Episode 10

Jeff is hired by a company to find out who is leaking information in the stock market. Finding Jeff suspiciously out of character — and also now being unable to see him — Marty finds out that the real Jeff has been captured and that the fake Jeff is an impostor, using his status to conduct murders of financial personnel. Marty uses a hypnotist to save the day.