They break up before they're ever really together.
It was lust, they told themselves, good old fashion lust.
Built on stress, fear, and comradely.
Even when Morgan confessed his feelings during a drunken slur, and Reid crawled onto his lap and kissed him for the first time, they knew it wasn't ever going to be.
After all it's just lust.
So they keep their mitts off each other at work, minus of course the footies under the table, or the holding each other's hands while no one's looking or even the longer then usual bathroom breaks.
They don't mention feelings or how long they might have possibly felt this way.
They don't talk about what could be, or what should have been.
After all, it's really just lust.
And when Derek smashes an unsub's face into the back of the SUV because he nearly killed Reid, (the bullet hit the wall seven feet away, but that's a minor detail), he still doesn't recognize what the feelings curling his mind into goo is.
Then when Reid ends up spending the weekend taking care of a flu ridden Derek Morgan, he chooses to ignore the way his stomach twists when he curls himself up against the other man and he slides his arms around his back. Even in sickness, wanting him close.
They break up four days later. Neither give a reason. God forbid they both say what they feel, god forbid they give it a shot.
After all, it's just lust. But love's so easily mistaken as lust.