Crime is terribly revealing. Try and vary your methods as you will, your tastes, your habits, your attitude of mind, and your soul is revealed by your actions.

The line expresses a core Christie principle: attempts to conceal guilt through cleverness or changing tactics ultimately fail because behavior carries an involuntary signature. In detective fiction, the criminal’s “method” may be disguised, but the underlying personality—preferences, routines, emotional reflexes—leaks into choices made under pressure. The quote also broadens beyond crime: actions, especially in morally charged situations, disclose character more reliably than self-description. It aligns with Christie’s frequent emphasis on psychology and observation: the detective wins not by brute evidence alone but by reading human nature and noticing the small consistencies that betray a person’s inner life.