A clone of Big Boss born through the 1972 Les Enfants Terribles Project, he was a manmade twin to Solid Snake, with whom he shared a virtually identical DNA signature. The fate he felt was coded into that very DNA fueled his actions.
He fought in the Gulf War as a teen, and infiltrated the Middle East as a sleeper for the British SIS (Secret Intelligence Service). He became a POW in Iraq, and went missing. Later, he joined Special Forces Unit FOXHOUND after Solid Snake had left it.
In 2005, he led FOXHOUND and Next-Generation Special Forces in taking control of a small Alaskan isle, Shadow Moses Island. There, he stole the nuclear-equipped bipedal tank, Metal Gear REX, and demanded Big Boss's remains from the American government.
In acquiring Big Boss's remains, he hoped to develop a cure for the disease caused by the Genome Soldier gene therapy, and to recreate Big Boss's Outer Heaven on Shadow Moses. The America military deployed Liquid Snake's twin, Solid Snake, in hopes of stopping Liquid.
Liquid used Solid Snake to his own advantage, however, luring him into disabling the PAL nuclear launch safety device. Although he successfully activated Metal Gear REX, the weapon was destroyed by Snake and the Cyborg Ninja, and Liquid's plan was foiled.
Ultimately, Liquid Snake falls victim to FOXDIE, the assassination virus the Pentagon planted in Solid Snake's body in order to quietly wipe out everyone involved in the Shadow Moses Incident, dying of a fatal heart attack.
But Liquid Snake's role continued even after his death. In the 2007 New York Harbor tanker sinking, Hal Emmerich used Liquid Snake's remains as a body double for Solid Snake.
Later, Liquid's remains were also transplanted onto Big Boss's body as replacement parts.