Perhaps a year and a half ago I promised I would get to "the doctor of death island" in a few weeks ... And I am finally getting to it, probably starting and hopefully finishing the write up in the next day or two.
I can't find the post, but someone asked if the consensus was whether or not Alvard is killed at the end. Rather than having to read my whole write up, which is coming soon, I will throw this direct answer out here a year and a half late.
The eight fingered dr, Margotte, survives unnaturally long - he is somehow death, though he shouldn't have lived long enough to get the immortality treatment. He is always at the prison when the white sheet comes, and his hyperthyroid eyes are the eyes of Alvard's partner Barry as he cast him out the window (probably for two reasons). margotte said he snoozed during the day but was always on duty when someone died in the prison, and later he shows up when Alvard is released in that final scene, saying he was cryogenically frozen. He is there as death for Alvard as Jessie kills him, her jealousy reborn. My final write up will be more thorough, as always. I felt bad for so poorly estimating how long the 70s fiction would take to get through.