Step 1: Understanding the Concept:
This question tests your knowledge of the plot of the story "A Question of Trust" and the characters involved in the main conflict.
Step 2: Detailed Explanation:
In the story, while Horace Danby is attempting to rob a safe at Shotover Grange, he is interrupted by a young woman dressed in red. She very cleverly pretends to be the wife of the owner of the house. By acting confidently and tricking him into believing her story, she persuades him to open the safe for her, after which she takes the jewels and leaves him to be caught by the police. Therefore, he was tricked by a clever young lady.
Step 3: Final Answer:
Horace Danby was outsmarted and tricked by a clever young lady.