TV Guide Investigation Discovery Monday

An effort to find Dena's friend Brandi promises to yield results, and discussions tell of a tense relationship right before Dena's murder. Did a secret endanger her life?

Buying goods from the comfort of home

Buying goods from the comfort of home

Buying goods from the comfort of home

Buying goods from the comfort of home

The morning of his wedding anniversary, Mike Williams went duck hunting. However, when he failed to return home, an all-out search was launched. This was the beginning of a mystery that took almost two decades to solve after his murdered body was recovered 17 years later

When a father-of-two suddenly vanished on the day before he was to start a new job, his friends hinted that he had led a secret life. However, matters remained unsolved for years - until a tip-off revealed the jaw-dropping truth

The investigation into 31-year-old Billy Smolinski's disappearance in 2004, which followed the discovery that girlfriend Madeleine Gleason had cheated on him. In 2012, Gleason sued Smolinski's mother and sister claiming they harassed, defamed and falsely accused her of involvement. However, police believe Smolinski was killed by someone related to Gleason, a suspect who has since died

The murder of grandmother Irene Kennedy, found dead in a park. A distant relative was charged with her murder, splitting her family apart, and it took years, another killing and a jail house snitch to bring the family back together

A case in which an obsessive video blogger, who shared every detail of the rollercoaster life she shared with her husband and their children, suffered a break-in during which the intruders tied her up, kidnapped her husband and executed him. Detectives soon discovered that someone had been keeping secrets

The case of outgoing 23-year-old Brandi Wells, who vanished in Longview, Texas, shortly after heading for a nightclub in August 2006. Her car was later found abandoned on a major interstate