Kaleidoscope Eyes — Graham Watkins

Married epidemiologist Sam Leo is drawn into a highly charged affair with a mysterious young woman he meets at the site of a traffic fatality. Sam's nasty coworker, a computer hacker, discovers the affair and blackmails Sam into helping him predict the next in a series of sex murders as part of a computer game he has created. A pathologist-friend investigating one of the murders impulsively buys an expensive kaleidoscope, which causes a sudden intensity in the stagnating physical relationship with her husband.