These are the titles of the 13 episodes: (Warning: They could be considered spoilers)1- Pilot
2- The Edge
3- The Way Through
4- Exit One
5- Incoming
6- The Truth
7- Smoke and Steel
8- Saved
9- Static
10- Identify
11- Seven Sacrifices
12- And Then There Was One
13- Shadows in the Cave
Episodes 4 and 5 really suggests that this is all a game and, as someone goes out, one comes in. It also suggests that someone had left just before Janet came in. But then what about the 6 others?
The finale's title is an obvious reference to Plato's allegory so the game must involve perception of reality by the hostages.