Spoilers ahead for The Red-Headed League.
In this Sherlock Holmes story, Holmes and Watson are recruited by a flustered pawnbroker, Jabez Wilson, who has been tricked into joining a fake society, the Red-Headed League. In reality, the society was just a ruse to get Wilson out of his house between the hours of 10 and 2. Whilst he was out, the criminal John Clay, who had taken a job in Wilson's shop, was digging a tunnel to the nearby bank. Wilson was supervised by Clay's accomplice, William Morris, who acted as the League's enforcer and who served to make sure Wilson never left the offices they had hired for him to use.
When Clay had finished the tunnel, Morris disbanded the League. Wilson came to the office as usual to see a sign that read:
The Red-Headed League is Dissolved
9 October 1890
Holmes is then able to guess the date when the duo plan to carry out their raid on the basis of this announcement.
"And how could you tell that they would make their attempt tonight?" I asked.
"Well, when they closed their league offices that was a sign that they cared no longer about Mr Jabez Wilson's presence - in other words, that they had completed their tunnel. But it was essential that they should use it soon, as it might be discovered, or the bullion might be removed. Saturday would suit them better than any other day, as it would give them two days for their escape. For all these reasons I expected them to come tonight."
However, wasn't this a daft and reckless move on the part of the criminals? Relieving Wilson of his cushy fake job at the office was sure to arouse his suspicions. Because of Wilson's despair at losing the job he ended up recruiting Holmes, which lead to the foiling of their raid. Wouldn't it have made much more sense simply to leave Wilson to keep his membership of the League until they'd made their escape? He would eventually put two and two together once his assistant disappeared and he stopped getting £4 a week for doing essentially nothing. It seems that they put an awful lot of work into creating this whole charade in the first place. Why didn't they maintain it for just a couple more days?
This misstep certainly doesn't fit with Holmes's judgement that Clay was one of the brightest criminals in London.
"Smart fellow, that," observed Holmes as we walked away. "He is, in my judgement, the fourth smartest man in London, and for daring I am not sure that he had not a claim to be the third."
What can explain the behaviour of Clay and Morris here?