La Clown was an assassin who could shapeshift into anyone she wanted.During the Lobito Island Incident BEAGLE feared their hidden Pythagoras research data would be brought to light, so La Clown was hired to steal it before the Leone Unit or Solid Snake and his allies could get a hold of it, then to cover it up. La Clown captured the HRT agent known as Teliko Friedman and trapped her in a giant board game style room of her creation. She then took Teliko's place and found Snake when he was about to be killed by Leone. Clown saved Snake by throwing a stun grenade at Leone and introduced herself as "Swallowtail" and a bringer of good fortune. Clown was briefly seperated from Snake while he confronted Dr. Flemming and overheard him telling Snake that he had the Pythagoras data and that Snake had another personality called Hans Davis. Taking advantage of both pieces of information, Clown shot Flemming, causing him to drop the encrypted data, though he escaped unharmed. She then insisted that Snake hand the data over to her by claiming that Snake couldn't trust himself while Hans Davis was a threat.
Clown and Snake later survived a battle with Leone at a warehouse and attempted to pursue Flemming to FAR under the intention of forcing him to decode the Pythagoras data for them. It was around this point that Clown fired at Snake and escaped from him with the data. Snake later found out that the person he had been working for was not Teliko, but the assassin known as La Clown. When Snake found the real Teliko at the giant board game, La Clown is presumably the one who blew the room up.
La Clown later attacked Snake and Teliko at FAR-B5; still using Teliko's appearance at this point so Snake had trouble telling the two apart (even making this harder by using her hypnotism to "create" more copies of herself). Snake and Teliko eventually managed to defeat Clown who claimed that having never lost to anyone before, she felt like letting him win just to see what it was like. But she never thought losing would mean dying. Clown told Snake the location of both Flemming and Metal Gear KODOQUE; claiming that if she died right there and now, it meant that she was not the hero since the hero was supposed to survive to the end. So she concluded that made her the villain and that the villain was always supposed take the hero's side right before dying. Clown told Snake and Teliko about her incident with her childhood fire and mentioned that Snake and herself cannot be controlled by "No. 16" as they are not "name-knowers" (people who know their birthname). Snake had trouble understanding any of this and Clown simply said "I'm Swallowtail...I wish you the best of luck, Snake".
After dying, Clown's makeup dissolved and revealed burnmarks shaped like swallowtail butterflies. Teliko recognized Clown's perfume and realized that she was the killer of her father, Collin Friedman. Snake and Teliko then took the Pythagoras data from her corpse and left her where she died.
