The Unbreakable Alibi
[Freeman Wills Crofts' Insp. Joseph French] "Una Drake, a capricious Australian, has challenged her fiance to crack two unimpeachable alibis. She wants to prove that she was in two different places at the same time. Despairing that Una will not marry him if he cannot guess how she managed this feat, Montgomery-Jones calls on Tommy and Tuppence for help."
13th story in the collection . First published in the Christmas issue of Holly Leaves in December 1928.