If they had made him a mandrake-man, then by what little he could remember and guess, they could make him obey them.
They could make him turn on his friends if they'd made him a mandrake-man.
mnli hypothesis: They could make him turn on his friends if they'd made him a mandrake-man. premise: If they had made him a mandrake-man, then by what little he could remember and guess, they could make him obey them.