This Is Not Happening shifts from describing infants in all-baby trios to the study of baby-only quartets. In so doing it takes up the challenge of moving beyond familiar cultural scripts which focus on individuals, couples, or ‘jealous’ threesomes. Extended vignettes show baby foursomes feature multi-member conversations, overlapping interpersonal routines, dynamics of linking and attacks on linking, moments of individuation, and cooperative ‘work’ to maintain cohesion, while implicating individual histories. These analyses highlight the inherent difficulties of interpreting the complexity of human agency in groups and the value of ethnographic methods and theory. This Is Not Happening also presents statistical evidence of group-level interaction in infant quartets – showing that, for example, how one group-member acts at time Q is significantly influenced by what two or more other group-members were previously doing at time P. The chapter concludes by examining the kinds of theoretical, cultural and emotional challenge infants’ participation in groups presents to the psy-professions.