Abandoned.

Three friends spend their time exploring lost and abandoned places, crumbling houses, forgotten tunnels, empty factories overtaken by nature. Over the years their days have changed and they slowly began to lose themselves and went a little insane, they've seen strange things: doors closing on their own, distant whispers, odd symbols scorched into walls. They always brushed it off as wind, animals, or imagination. But on one trip, deep inside a place hidden from maps and memory, they find something they can't explain and this time, ignoring it isn't an option.