In the mirror universe, 2155, the Tholians detonated a tricobalt warhead inside the gravity well of a dead star, creating an interphasic rift to the year 2268 of the prime universe. Unwilling to explore the rift themselves due to the dangers, the Tholians transmitted a distress call into the rift in an attempt to lure a ship from the other side. The distress call was detected by the USS Defiant which subsequently became trapped in the rift. As a result of being exposed to interphase, the crew began to suffer from a distortion of the brain tissue in their central nervous systems, which manifested itself as violent and paranoid behavior which ultimately led the crew to murder one another.