'Keepers' can mean someone who is responsible for looking after or protecting something or someone. So it could be a synonym for 'guard', 'bodyguard', 'custodian', 'protector', etc. It is not a word that can be used in every context, but is often used when talking about a zoo or a wildlife park, because animals need to be looked after (they can't do it themselves). I think that is why it is also often in a police/crime context to talk, with a slightly negative sense, about a person who needs protection because the speaker thinks they can't look after themselves or maybe don't have the freedom to look after themself. Is the character they are talking about not able to do things on their own for some reason?