Meg Cabot

The half smile Paul had been wearing vanished. His face was as expressionless as the wall behind him.
"So that's how you're going to play it," he said.
I had no idea what he was talking about. " Play what ?" I asked.
"I could do it, Suze," he said. "It can't be hard to figure out. And when I do... well, you won't be able to accuse me of not having stuck to our agreement."
"What agreement?"
Paul set his jaw.
"Not to kill your boyfriend," he said tonelessly.