“Improbable Cause” is episode twenty of season three of Star Trek: Deep Space Nine.
Garak’s shop on the Promenade is destroyed by an explosion, but he manages to survive largely uninjured. When Odo investigates, he discovers it was a bomb that destroyed the shop, not an accident. Odo’s investigation leads him to a possible assassin, but when he and Garak – for the latter insists on accompanying Odo – follow the assassin’s ship in a runabout, it explodes as it enters warp.
It seems that the assassin was killed by the Romulans, something they readily admit. Odo’s sources on Cardassia reveal that five former members of the Obsidian Order have all died recently, from ‘natural causes’ and ‘accidents.’ Along with Garak, they were all associates of Enabran Tain, the only head of the order to survive until retirement.
Gatak still has feelings for his former mentor, so accompanies Odo again as they look for him.
The story continues in the next episode, “The Die is Cast”.