"Sleep" was just a quick, painless death from the usual tormenting styles Beato uses. After death, any of the bodies can be rearranged to look like murder.
There's nothing wrong with Virgilia turning back to Kumasawa, since it satisfies the 18 persons on the island requirement.
Despite the fact that there is a definite element of mystery, the anime does not portray all the facts to make a logical conclusion nor even a definite statement. If you really want to solve the mystery, you will have to read the sound novel, Frosty. You're not getting anything here, and everyone else is just watching this for the kicks.
Last edited by Beato; 10-03-2009 at 10:37 AM.