There were a few around here before with the ability to see souls. Apparently, when death occurred, rather than being severed from the body, the soul hung around and waited until the healers were able to bring body and soul back together. You can choose to believe me or not; the murder victim has since vanished from the island.

As for the experiment, it would involve a capability I possess as a Summoner of spirits. If you, Ratatosk, are merely a spirit sharing the body of this young man, a contract may be possible. If you're a split personality of some sort, it'll be a no go.