Detective Conan S01 E778 Mirage of the Disappearing Angel

"One truth prevails."

A woman asks Kogoro to find her missing husband, who went to an unknown location to draw and has stopped communicating with her. Thanks to the last picture he sent to his wife, they are able to find the location. When they arrive, they find the missing man dead, with his painting being the only clue of who the culprit may be.