In the novel N or M?, Vanda Polska is a middle aged Polish refugee woman. Tuppence first encountered her loitering outside the Sans Souci hotel at Leahampton. As Tuppence was on the look out for every agents, she was naturally suspicious of her. Her suspicions increased when she caught sight of the woman casing the hotel from behind bushes.
Later, Mrs Sprot discovered that her baby Betty had gone missing. With the help of other hotel guests and the car of Commander Haydock, they searched the town and caught up with Vanda with Betty walking away from Leahampton along a cliff top path. Vanda refused to give up the baby and looked like she was about to throw the baby over the cliff or jump over herself. Mrs Sprout shot with a pistol and in what appeared to be a lucky hit, killed Vanda without hurting the baby.
Testimony by Mrs Calfont and Inspector Brassey served to cast further suspicion on Vanda. Still, Tommy wondered why, if she was a fifth columnist, she should bother to kidnap a baby.