They say keep your friends close...and your enemies closer. But sometimes those you've trusted to watch your back are really just looking for the right place to plunge the knife. True stories of trust so easily twisted. Double Cross... all new series Thursday at 9pm. Only on Investigation Discovery.—Investigation Discovery

When a murder investigation leads to the ex-wife and no physical evidence is present,detectives must find a way to solve the case. While in character as a disgruntled cop,detectives learn this isn't the first husband to die while married to this black-widow wife.—anonymous