Let’s say you have a haunted house and a group of unsuspecting teens. Would you rather watch the movie where they go one at a time into the haunted house, or would you rather watch the one where they all go in together?
Either way, you’ll get your scares, your gore, and plenty of screaming. However, if they go in together, you also get character conflict.
Picture that moment where the group stands in the main hall of the massive haunted mansion, everyone’s eyes darting around to check the shadows for something sneaking up on them.
“We need to get out of here! Does anybody remember how to get back to the entrance?”
“No. These spirits aren’t trying to hurt us. They must have some unfinished business. Maybe we can help them cross over.”
“You’re nuts. Ghosts aren’t even a thing. I think I saw a sword and some other weapons back in one of those rooms. Whoever’s doing this is gonna wish –”
“They’re. Not. Human. We’re dead. We’re all dead.”
By forcing these separate individuals together with their different viewpoints on what’s going on and what to do about it, you’re not just creating additional conflict for the characters to deal with, but further defining each character for the audience. The more we know about the character, the more we attach our hopes and fears to their actions. This isn’t just about learning facts about the characters that endear them to us, but about seeing how they behave under pressure, and seeing how that behavior reveals their character.
It also applies outside the horror/slasher genre. Taking characters that don’t always get along or agree and jamming them together is a way to build tension in any genre. Ferris Bueller’s Day Off wouldn’t have been nearly as exciting if Ferris wasn’t working to get Cameron to loosen up. In The Godfather, does Sonny Corleone decide unilaterally how to deal with Sollozzo and Captain McCluskey after the second attempt on his father’s life? No. Michael, Tom, and Sonny are all in the room together hashing out the decision, and the existing conflict is magnified by the friction between their personalities.
If you have characters whose personalities rub each other the wrong way, are you doing everything you can to force them together? If you have characters that already spend a lot of screen time together, are they too often on the same page, or is there room to create friction between them?