So i was running a game set around the fae, set in a sort of blend of the Dresden Files universe and The Secret World. A summer fae hired the Phoenicians (Kind of a much, much less scrupulous version of Monoc Securities) to kidnap Jack Frost and the Green Man of the Spring during the solstice to interrupt a ritual to end summer and begin winter in the world.
We had four players, only two of whom are relevant to this story. We'll call them Player 1 and Player 2. Player one was an active member of our group, playing a sort of elementalist/spirit talker who communes with the elements, and also the face of the group. Player 2 was married to player 1 IC'ly and OOC'ly, being her husband, and was clearly just along because his wife asked him to come. For the opening first half of the starting session he pretty much said nothing, when intereacted with he mostly shrugged and murmured something non-commital. I was cool with this, he made it pretty clear he didn't much want to be here (Although he was never rude about it) and i didn't want to force him to play if he didn't want to so i eventually stopped trying quite so hard to get him involved.
Anyway, right at the end of the game the party came across a squad of phoenicians out in the woods with a campervan, having crashed into a ditch. The party came along pretending to be passers by looking to help whilst really looking for clues inside the van, and a social encounter started, the party trying to keep up the act of just being some passers by (And finding nothing but a bunch of digging equipment, like shovels and whatnot). Player one failed a few rolls and one phoenician punched her inside the van and drew a gun. At this point we hear a voice, IRL, going "I hit the phoenician on the back of the head with a shovel".
It was player 2, and i swear to god everybody looked around for a moment or two wondering who was speaking, because nobody had heard him properly speak all game. He continues "They had digging equipment right? So i hit him on the head with a shovel". As it turns out, there is ONE way to get player 2 to take part in the game: Threaten his wife, if only ic'ly.
A roll later and the phoenician is unconscious and the other slips away (There were only two), and the group decide to question the phoenician and player 2 goes into full-on "Psycho cop" mode, putting a bucket on the phoenician's head to blind him, striking the bucket a few times and, i quote "Saying things like 'if we don't get home soon to watch Downton Abbey i'm gonna snap'". The poor guy never stood a chance, and spilled everything he knew more or less on the spot.
P2 sadly seems to have gone back into "Non-commital murmur" mode, and we've gotten very little out of him since, but it's only been one session since then, and if i ever want to get him involved again... i now know what to do