When first seeing Son of Mine, Mother of Mine, and some Scarecrows outside the school on 11 November 1913, his immediate thoughts were that "some practical joke has got out of hand". Rocastle then realised the Family's true colours after Son of Mine vapourised bursar Phillips with his energy gun, causing him to make a hasty retreat into the school, much to Mother of Mine's amusement.
Later, he made a fatal mistake when after a fight with the scarecrows, Daughter of Mine, a member of the Family of Blood appeared at the door and Rocastle, unaware and disbelieving of Martha Jones and Joan Redfern's saying of her being part of the Family, chose to invite her into the school for her own safety. Daughter of Mine promptly vapourised him with her energy gun. (TV: Human Nature / The Family of Blood)