Probably, but do you really want to owe him another favour? We can get one from somewhere else, I know someone.

[Someone he once did a turn for who owes him a favour, not that he cares about that and nor did he at the time, it was just that their case had been interesting.]

You could walk away from this now, John. Your sister's killer is gone, you are no longer a target, and you require medical attention.

[There's a tiny almost imperceptible smile at his lips as he makes that suggestion, because he knows full well that John won't back down. It's oddly nice, having someone by his side in these cases.]