I need help with my novel... How would...?

Sounds like all he has left to use is his brain. Try to think of ways the kidnapper can trick his victim to get in the car. The victim might have weaknesses which can be exploited. How this plays out really depends on your characters and the story. (victim's mother left home years ago and all he wishes is to see her again, which the kidnapper knows, so he claims he's been sent by the mother - she can't come herself because blah blah blah and the victim should come with him to see her) ok, that's not very imaginative, but it's not my story.