Drew hates labels, but loves Halloween and he wants a trick-or-treat of his own. At his mother's to deliver emergency candy, she has him get the door in his gender-bending costume. The handsome man with the little trick-or-treater would be Drew's perfect treat.
David's attraction to Drew is no trick. He wants the whole Drew, in all his unlabeled glory, making Drew think this could be a treat that lasts long past the holiday.