Although Wolfe's investigation begins unpromisingly, he becomes convinced that his suspicions are correct when the police receive an anonymous tip revealing Laidlaw's secret. Although the police are skeptical due to the tip's anonymous nature, it suggests to Wolfe that someone else knows Laidlaw's secret and has become agitated by the ongoing investigation.
Although Wolfe's investigation starts off poorly, he becomes convinced that his suspicions about Laidlaw are correct when an anonymous tip leads the police to uncover Laidlaw's secret. The police are hesitant to act on the tip due to its anonymity, but it suggests that someone else is aware of Laidlaw's secret and is likely upset by the investigation.