Whose death leads Ira Wells (Art Carney) to team with Margo Sperling (Lily Tomlin) in The Late Show (1977)?

His former partner Harry Regan’s (Howard Duff) death leads Ira Wells (Art Carney) to team with Margo Sperling (Lily Tomlin) in The Late Show (1977).

Regan had been hired by Sperling to locate her missing cat.