Lisa Tu disappeared without a trace on July 14, 1988, in Potomac, Maryland. Her common-law husband, Gregory Mung-Sen Tu, claimed that he had put her on a flight to San Francisco that day, but she never arrived. A ticket to San Francisco was found in Lisa's name, but her seat was empty. It later emerged that the person she was supposedly visiting was in good health and had not heard from her in months.

Investigators discovered that Gregory had paid a garbage collector to dispose of a loveseat from their residence two days after Lisa vanished. Investigators believe that Lisa's blood was found in the basement, where the loveseat had been. They also found a meat cleaver, twine, and plastic wrap in Gregory's car, along with blood on the dashboard.

Gregory withdrew $44,000 from Lisa's son's college fund without her permission just five days before she vanished, and investigators believe Lisa found out and argued with him about it. Despite Gregory claiming to have a good relationship with Lisa, others say that they frequently argued, usually over money, and Lisa had been considering kicking him out. The couple's house was in Lisa's name only, and Maryland did not recognize common-law marriages, so if Lisa decided to end the relationship, Gregory would have had no rights to her property.

Lisa was financially stable, but Gregory was having financial difficulties. He was convicted of second-degree murder in 1992, six years after Lisa's disappearance. Prosecutors believe that he shot Lisa inside their home. Gregory still remains incarcerated, and Lisa's remains have never been found.