The Mod Squad S02E23 - Return to Darkness, Return to Light

Janny Wills, first introduced in the first season episode "A Hint Of Darkness, A Hint Of Light", invites Linc, Pete, and Julie to meet her new fiancé, Dr. Frank Tarver. Tarver doesn't tell them that he is being threatened by a man blaming him for his daughter's death. But when the trio investigates further, they find that Tarver may not be who he seems.