Revenge corrupts even good people.

Many years ago John took advantage of you. He knew he was a bastard, but damn, you were the teacher's kid. He really needed to pass the exam. He dumped you right after school graduation.

After that you slipped some molly in his backpack and called the cops. He was almost refused admission to the SAS, but he proved his innocence.

When today it turns out that you are a new team member, he almost growls at you.

"Dinnae come within a fckin meter o' me."