Portals (4): Planet Aya contains many mysteries, as Aya and her friends soon discover. They find a machine capable of creating items out of thin air. At least, that's what it claims to do. However, before this claim can be verified, the scientists need to work out how to operate the alien machinery. Then, much to their puzzlement, a room of multiple doors is discovered by the exploring group. But the doors don't open to anywhere. In fact, they're all attached to a solid cliff face, which seems to defy every strand of known logic. Why build doors that don't lead to anything?
The answer to this mystery is solved by another one of Aya's dreams. Actually, it's only partially solved, because the dream taunts her by being only fragmentally remembered. Aya finds this situation to be extremely frustrating, especially when she notices the others looking at her in eager expectation. This tension reinforces her feeling of anxiety, which erodes her self-confidence. However, when the remainder of the dream arrives, and provides the final answer to the mystery of the doors, what will it mean to the human occupants of the spaceship? And, most importantly, what will it mean to Chance, the alien hybrid in their midst?