He claims to work for the government, says her father invented a biological weapon and he has to find it first before they do.
It's a dirty lie, so she doesn't feel guilty leading him on a wild goose chase while awaiting a chance to escape.
But he wasn't lying when he said there would be others after them with deadly intent. And she soon learns that he has secret motives born of an unthinkable loss, that might just have been a lie.