Derek's hands shook as they clutched the wheel, causing the car to swerve and jerk at small increments; he frowned, tensing them further in a futile attempt to control himself.
He knew what was happening and how the shaking wouldn't stop until he fulfilled this need, this debt. Figuratively, he owed it to himself to do this, to give into the urge, but he literally owed it to Stiles, because Stiles saved his life and the wolf inside him couldn't let it go. His kind were required to pay back good deeds, bound by instinct and a pack bond. Scott was his beta and Stiles' carried Scott's scent.
For the moment, Derek was glad to focus on the shaking instead of the pulse of anger at the idea that Stiles carried Scott's scent rather than his own. He didn't have time to deal with that petty thought, instead he had to devise a plan to protect Stiles from the showdown about to happen at the rink.
It was then that he decided to call Erica and tell her just what she owed him.
Really, he couldn't have known that she would do more damage than good.
He knew exactly when it happened, though, as his entire arm twitched, and he had to wolf out just to control his body and his impulse to run.
And to think, life debts evolved as a survival tactic.
Still, he couldn't do much for this debt when he had betas to train, especially when Stiles kept on increasing the debt as he took care of Scott who teetered on the edge of packmate and omega. He didn’t know how, but he would have to take care of this life debt in one act. It was more than likely this new creature would make it happen, as Stiles and Scott had a habit of attracting everything they couldn’t handle.
Like the Argents.
Anyways, it was later when he was confronting Stiles about this new creature when the opportunity arose (and, of course it really was that goddamn creature). He pushed Stiles out of the way, saving his life and fulfilling the debt.
And then Stiles held him up in the pool for two hours and risked his life getting the phone.
Derek was pretty sure the only reason his entire body wasn’t twitching at that point was because of his paralysis.
For some reason, fate decided that Derek was meant to spend more time with Stiles. Derek didn’t even know if he was okay with this—Stiles was irritating, with his constant snark and need to one up Derek. Derek was an alpha, no one was allowed to one up him anymore. Who was some button nosed kid to stand up to him?
Well, Derek was just going to have to find out, as he set upon following Stiles to ensure that he’d always be safe. Of course, this was just to fulfill the life debt.
That is why he always turned around whenever Stiles changed or spent an hour and a half watching porn and ignored the sound of moans and grunts as they drifted into his ears through the window. He never entered the house or moved past the front yard. He never told Stiles about the debt, knowing the smartass would just try to find a way to solve it himself, which would just extend and empower the debt. He never told anyone.
He just watched and waited, his stomach crawling a the idea of failing and Stiles getting hurt, and his arm twitching in continuous waves, the spasms worsening every time Stiles bumped into his father and avoided his gaze or watched Lydia Martin walk away.
There were too many things to save him from and yet not enough to do. This was Derek’s life now, helplessness in the face of duty.
This would always be his life.