The inability for someone to see past the first step in a plan, thereby being clueless as to what to do when it is successful. So named because indoor cats always pine to go outside, staring out the window all day, trying to sneak out the door, but once outside, they have no step 2 to the plan.
This one guy was planning to kill his wife for insurance money, but once he did, he had no idea what to do next and was caught quickly. He really had Indoor cat syndrome on that one.