Ghost Inmate is one of the five endings to the game Fleeing the Complex. The name most likely refers to the fact that, upon reaching this ending, none of the guards in The Wall have noticed yet that Henry is gone (identical to the Undetected Ending of Stealing the Diamond).
Getting the ending
To reach this ending, one has to choose "Boost Up" in the start screen, but then choose to abandon Ellie and continue solo.
Henry proceeds to make his way towards The Docks, slipping past multiple security guards and going down an elevator shaft. When he reaches the docks, he steals the Dinghy and sails off into the night. The two guards at the docks see him, but mistake him for Smith and thus don’t raise the alarm. During the end credits, Henry is seen sailing the dinghy.