On his way home from work, Thomas Prescott stops to pick up a hitchhiker who claims to be going to visit his doctor. However, when he arrives at the destination, the mysterious man attaches a strange bracelet to Prescott's wrist, pulls out a gun and reveals that he knows an awful lot about the driver. Prescott is told to go to his office and find a certain file, which contains the key that unlocks the bracelet, then leave the bracelet behind. The bracelet will explode at eight o'clock pm, so he is encouraged to hurry as it is now twenty minutes to the hour.