Summary:

Harry Potter has one inappropriate thought about Draco Malfoy, ONLY ONE. Unfortunately, magic is a petty bitch and it notices.
The next morning, Harry wakes up with a soulmark on his inner thigh: a bright red S+, placed exactly where no decent person should ever be formally assessed by Draco Malfoy.
Draco, meanwhile, has no mark at all: only an ache, a deadline, and absolutely no idea that the soulmate he is looking for is the man he keeps insulting.