My younger brother, Steve, and his friend James perform an experiment on me, Jeff, and the Younger Dan. They inject brain tissue solution into each of us, causing us to each grow a second brain. Each brain had its own personality still, however. Mine was named Derek; Jeff had an Aztec diety of some kind. Don't recall who Younger had.
We wandered around a facility that was part Travel Lodge and part elementary school. Eventually, "Derek" manifested himself a body and split off from me, to wander the corridors by himself.
Kevin Matthews, a techie from the community college drama department, showed up; he'd been recently reunited with his estranged father, who worked the facility as a laboratory. At the time, it seemed natural, but later I was struck by a strange suspicion that I couldn't quite place....