The introductory music still sends chills down your spine.

Nearly 40 years after it debuted on television, “Unsolved Mysteries” still is known as much for its eerie composition as any of the stories it told.

(Cue the music. If only host Robert Stack were alive to slip on a trench coat and read an ominous script.)

As the fourth Sunday of the season gets underway, these are some unsolved mysteries creating buzz around the NFL.