I’ve always enjoy a story more when a writer doesn’t just spring a surprise on me (deus ex machina) but builds up the characters in full view of me but not from each other.

Had Nostromo just ‘turned up’ at the barracks before the doctor and the unfortunate victim, the story would have been almost silly – be we knew Nostromo was alive, how he stayed alive, and that he has other secrets from the doctor.