1. Only believe in facts. Each fact must prove the existence of the occurrence.

2. Verify everyone’s behavior patterns.

3. Verify that everyone’s language answers are not inconsistent, and everyone’s language must be self-consistent.

The murderer's motive in "Tragedy on the Nile" is love. Simon and Jacqueline truly love each other but are in trouble materially. Therefore, Jacqueline had no choice but to temporarily give up her sweetheart Simon to Lint for the sake of future "happiness". Simon married someone she did not love just to get her property. So they conspired to direct a murder for money.

Extended information:

"Death on the Nile" is a novel by the British writer Agatha Christie, first published in November 1937. The story revolves around the investigation of three murders on a yacht on the Nile by Belgian detective Hercule Poirot, who eventually brings the tourists together to reveal the truth behind the three crimes.

In "Death on the Nile", Linbait is the "queen" of the scene, and is praised by people wherever she goes. Regardless of appearance, wealth, or personality, Lin is the most attractive woman, attracting countless customers under her skirt.