Heel sound

Exploration Stage: Crash Site
From: Inspector
Description: Do you really believe that the glittering actresses that Case dated had spies in their midst? They had no respect for Case's talent. He had accomplished so much! To their surprise, they found one of Lady's high heels by Case's plane. I'm beginning to understand what's going on. Can you help me find the other shoe?
Completed: There is a slot in the heel of this high heel. There's a cryptograph in it! These are Eve Garden's high heels. She's one of the beauties in the case... she was both beautiful and cunning.