Tommy, Beauty, and Baby had set up a harmonious household when a pet store offered an irresistible bargain in the form of an additional pair of young marmosets that nobody seemed to want because they had been injured at some time, the female losing a couple of inches of tail and the male two or three fingers from one hand. This led to a lesson in the social customs of marmosets. Beauty had not in the least minded sharing her home with Baby, but with the appearance of the newcomers there was trouble.

It began with Tommy, who apparently…