One of Sherlock Holmes’ enduring tropes is the dog that didn’t bark in the night, giving away the fact that it knew the intruder. It’s easy to notice what happens, but far harder to notice the telling thing that doesn’t happen when it should.

In mid-February, a US intelligence chief confessed on prime-time TV to plotting with other top Washington bureaucrats to knock off a president, Trump, with much the same tone you would use to discuss an annoying staff meeting that was keeping you back at work late.