Captain Embry crashes his WW2 prop plane in the desert. The rest of the crew is gone, and Embry doesn’t know what has happened. He hallucinates, sees and understands technology of the future, and concludes “There’s not a single thing that’s real.” Like “Where is Everybody” this is the case of an extended illusion, brought on by military experience. In this case, Embry, who was responsible for the ship and its crew in 1943, relives the horror of the crash that killed his crew. He survived because he wasn’t on that mission.
So there’s Embry in bed in the pscyh ward, and Embry with the downed King Nine in the desert. We know which is real, and which is the illusion. But Embry’s hallucinations are causally related to the real, to the facts of the downed aircraft and the fate of his crew members. The point is driven home in the final minute, where Embry’s clothes are brought into his room, and there’s sand from the desert in his shoes.
The observation that the illusory builds on the real is noted in other episodes, for example, it is emphasized in “Shadow Play” where the lead character has to convince everyone else that what they think they are experiencing is just a dream. He does that by showing how the experiences they are having are constructed and rearranged from his contents of his imagination, which draw on his actual experiences of the world.
Why is this philosophically or otherwise important? The example counts against the view that the products of the imagination are pure imaginings – pure products of unfettered thought. They are instead grounded in experience, not just by being constructed out of what we’ve sensed and perceived, but more thickly, from rich experiences and matters we’ve thought through and understood.
The sand in Embry’s shoes symbolizes this. He isn’t just a soldier who has “lost it.” Rather, he’s retained it, and that’s what haunts him and causes him to construct an imagined world that’s too close to the actual one.