Allie Jamison was a girl who lived in Jupiter Jones's neighborhood. She appeared in two books, both by M. V. Carey: "The Singing Serpent" and "The Death Trap Mine". She was often a nuisance as she always wanted to do case-solving with the trio but also proved to be useful. In The Singing Serpent she found a bomb disguised as a walkie-talkie and in The Death Trap Mine she found the corpse that lead to the mystery.
Allie was an only child who lived with her parents, though one cannot exactly say so because her rich parents were often away on business trips and during her first appearance in the series she is living with her superstitious Aunt Pat. During her second appearance she is on vacation.