The Fiend at the Throttle

Federal agent Alexandra Barnes believes that Catherine Petersen is a serial killer who marries rich men and then murders them for their money. But since Catherine is seemingly a master of disguise and has multiple identities, Alexandra can't prove anything with conventional detective work. With no other option, she goes undercover, pursuing the same man as Catherine, and hoping that Catherine will slip up and reveal her true identity.

When hired killer John Gant rides into Lordsburg, the town's folk become paranoid as each leading citizen has enemies capable of using the services of a professional killer for personal revenge.

Young socialite Iris Carr befriends an older woman while traveling solo by train. When Iris wakes from a nap, the woman is gone and other passengers claim she never existed.

Two couples vacationing together in an R.V. from Texas to Colorado are terrorized after they witness a murder during a Satanic ritual.

A member of British Intelligence assumes a fictitious criminal identity and allows himself to be caught, imprisoned, and freed in order to infiltrate a spy organization and expose a traitor; only, someone finds him out and exposes him to the gang...