Since it was Halloween, you lacked the outfit to wear at the party when you saw the other guys wearing costumes during the holiday season that would make the party work. Just then, you spotted Mark head to the costume shop, because he didn't have a costume for the Halloween party either, so you decided to do the exact same.
As you follow Mark into the costume shop, you noticed a sign out front before going inside that would explain the price of how much the costumes were, saying that they were 75% off. You were curious of why a costume shop like the one you saw Mark go into had a very convincing discount, but you didn't exactly care as you went inside. Mark was out of your sight, and was probably in the dressing room after choosing a costume, which leaves you to choose one, but you were going to need help.