"Have you just said you'd leave me in a ditch if I caught a bad cold?" Porthos asks, lips twitching, because he's done the serious thing for a second there, and falling back on humour now only feels natural. "That's good to know. Not to worry - you won't be rid of me any time soon," he adds, to let Athos know that, teasing aside, the sentiment is appreciated, and reciprocated.