Lying
I was, at least at the start of this disastrous game night, your friend.
I was, at least at the start of this disastrous game night, your friend.
Mafia (and other games such as Werewolf) is a party game centered around two opposing teams who must eliminate each other: the mafiosi (or werewolves, accordingly) whose aim is to secretly gain a majority and the ordinary players (who may be termed 'townies' or 'villagers') who have to resist this. While the mafiosi know who are mafiosi and who are villagers, the villagers do not know any other person's role. The mafiosi also need to keep their affiliation secret from the villagers so long as they are outnumbered. The game alternates between day and night phases. During the day, all players vote on which suspected anti-villager should be 'killed' (removed from the game). During the night, all surviving members of the mafia decide which villager should be 'killed' to further their own purposes.
Play can be undertaken in person or across a suitable online forum/group-chat, whilst similar mechanics have been adopted for networked games such as Town of Salem, Among Us and (in combination with other mechanics) Space Station 13.
Here we have Cueball (possibly Randall), Megan, Ponytail, and White Hat sitting at a table, apparently playing this type of game, in which some sort of secret must be maintained by lying. Cueball seems to have been unable to maintain the lie and came clean, perhaps hoping that they would remain friends, somehow fearing that playing the game as required would lose him the friendship that brought them together to play the game in the first place. The other members are annoyed by his undermining of the basic concept of the game, and White Hat offers to switch to playing another game called Taboo. This may not improve things; given Cueball's apparent inability to maintain secrets, he may feel compelled to tell them the word concealed on his card, and thereby immediately lose.
The title text could both be referring to what Cueball says about how the others are his friends, and also that the others could have gotten so annoyed that they stop being his friends. It is clearly very similar to Spock's dying words in Star Trek II: "I have been, and always shall be, your friend".
In reality, Cueball could actually be cleverly playing one of a number of other roles that a mafia/werewolf game can have. There are additional player-types that win by being voted off (often this must be a day-vote, a night-vote by the 'bad guys' is a loss), and others that make the player invulnerable to votes in certain conditions, make the 'kill' act upon another player and/or result in assisting those in a further 'team' of conspirators. Though usually such complications aren't included in gaming groups with as few as four players, and they usually rely on bluff (or multiple layers of bluff) against players who are aware of what they entail.