Foundation series
Both Turner and the Mule from the Foundation series are discovered and stopped due to very similar mistakes. The Mule could not bring himself to touch the mind of Bayta Darrell, the only woman who cared about him (and whom he seemed to love), leaving her free to piece together the clues about his identity. Similarly, Turner is exposed because he couldn't bring himself to disturb his dearly loved wife during the supposed danger to the city, despite their house being equipped with a shelter for such occasions, which made Starr realize he knew there was no danger in the first place.