When Mac is scheduled to take a first-class flight from San Francisco to Hawaii, an airline executive arrives early and in mechanic's garb on the pretext of inspecting the aircraft. His real mission is to poison his wife, via cyanide injected into a champagne bottle. But a drunken passenger clamoring for more gets the lethal dose by mistake. The plane develops serious engine trouble and turns back to Los Angeles. The executive goes up to the VIP lounge to await justice -- but it comes sooner than expected when someone follows him upstairs and stabs him. Mac and a flight attendant team to try to find the killer, who may well be a member of the flight crew.