About fifty minutes into the film, the plane shown landing is different that the one Smith is shown getting off. Both are Bristol Type 170s from British United Air Ferries, but their tail markings are completely different and the first is a Mk 32, and the other is a Mk 21.
The apartment building Chris Smith looks at before he arrives at his eighth-floor penthouse doesn't seem to match reality (elevator shows only seven floors plus penthouse level).
The elevator buttons at Smith's luxury apartment building show 7 floors plus the penthouse floor being the top, but in the external shots it's obvious the building has more than eight floors.
At the end of the movie Chris is packing up with Gina when the private detective arrives and tells them that the lady and gentleman have been delivered to the appropriate authorities. The apartment is a crime scene and there are no police and there is no explanation as to where the corpse has ended up. Yet they all just walk out of the apartment at the end.
A pulse is visible in the neck of the first 'corpse' found in the shower.
It is inconceivable that British Customs would not have checked the trunk of the car, having just been flown in from France.
When Gina arrives and Chris shows her the body, instead of phoning the police or Dr. Keller, Gina goes to the doctor's house to fetch him. Logically she would have phoned him to confirm he was home and available.