Before the Great War, Lou was an engineer who lived in Pittsburgh. He was 70 years old when the bombs dropped, making him nearly 100 years old in present time. Rumors around the Crater say that an atomic bomb fell straight into his living room, but it was a dud and failed to go off. This was the origin of his nickname "Lucky Lou," a reference to his ability to turn a curse into a blessing, and he went on to defy death in at least a dozen more incidents. As the radiation poured into Pittsburgh, Lou became a ghoul, something that has haunted him ever since.
After Lou joined up with the raiders, he became respected by people like Meg Groberg, Caleb Fisher and Weasel, even if some of his friends were disgusted by his appearance. Lou was one of the few people to play with Ra-Ra when no one else would and she views him as a friend. He lived in a small room resembling a bunker in the underground area of the Crater Core.
Although many of the Crater raiders would take a bullet for Lou, his worries of turning feral spiraled him into deep depression. These feelings were planted and amplified by Lev, who despised ghouls and wanted Lou in particular out of the way to sabotage the raiders' heist plans. Not wanting to take any chances, Lou would rather take his own life over possibly going feral and attacking his friends. He left behind a goodbye note entrusting his belongings to Fisher, showing the depths of their friendship, and went to hole up in Carleton Mine in order to find a decent way to kill himself.
Unable to simply "pull the trigger," Lou constructed a number of death traps that would result in his demise, including a machine-powered shotgun blast, several automated turrets scavenged from the ATLAS Observatory, and even a makeshift building that would collapse in on itself. However, none of these contraptions worked despite multiple trials, living up to Lou's status as someone who would always cheat death. Left with few options, Lou decided to take the last resort of simply detonating explosives. If the collapse of the mine would not kill him, then at least he would be trapped inside and unable to hurt anybody.
Cheating Death: As a demolitions expert, Lou is needed for the Vault 79 heist. However, he is missing from the Crater, and his location - Carleton Mine - must first be discovered, then he must be tracked down in the mine and convinced to join the crew. Lou agrees to join on the condition that the Vault Dweller helps him commit suicide after the heist.
From Russia With Lev: Lou was attacked by Lev's gang in the cavern entrance of Vault 79 and left to be killed by a yao guai; he must be rescued, and then his remote detonator for the explosives on the Vault door must be recovered from Lev.
Buried Treasure: Lou triggers the explosives to bring down the Vault door and enable the start of the heist, then stays outside with Meg Groberg, ostensibly to ensure the stability of the area.
If Lou is spoken to in the Crater Core, he will mention that he is trying to offload his explosives and offer a random grenade or mine.
After completing Secrets Revealed, Lou can be spoken to about his previous deal with the Vault Dweller, where he will voice his hesitation to go through with suicide. All options in the conversation will eventually lead him to conclude that he is determined to go on living, and the player character will gain a small amount of raider reputation. Afterwards, he will continue occasionally offering random explosives.
Lou's vocabulary is filled with Pittsburghese words such as yinz (a plural form of "you"), n'at ("and that"), and jagoff ("idiot").
"In case it ain't obvious, I'm one of them rad-soaked ghouls. Been that way goin' on twenty-five years. Ain't no way to live. Killin' myself's the only way to keep people safe. Course, that's harder than you think."
Meg Groberg has unused dialogue revealing that there was an original intention for Lou to potentially die during the vault raid, particularly at the hands of someone. However, in the final quest, only Johnny can die and Lou remains in the entrance area. If only Lou died, Meg would say, "Losing Lou is a real bad deal. You shoulda come to me on that one Seven-Six. I know it's what Lou wanted, but I can't say I approve." If both Lou and Johnny died, Meg would say, "Losing both Lou and Johnny is gonna take its toll. 'Specially since we coulda helped Lou... but someone took that choice away."
↑ 1.01.1Vault Dweller: "Why's he called Lucky Lou?" Meg Groberg: "Least when it comes to dyin'. Lou's got a knack for cheatin' death. He was up in Pittsburgh, 70 years old, when shit went down. They say a real honest-to-goodness A-bomb fell straight in his living room. Thing didn't go off. A dud." (Meg Groberg's dialogue)
↑Caleb Fisher: "He's always a little surly. It's possible it's on account of his condition. But, he's had years to adjust. Sure, some of the others don't like the way he looks, but they still respect him. I say, I don't know a soul who wouldn't take a bullet for Lou. Not that he needs it. Every curse somehow turns into a blessing for him. However, because of his condition, Lou is frightened that he will eventually go feral. In fact, if I were still a religious man, I would say God watches over him and has special plans for Lou here on this Earth. Lou's one of the luckiest men alive. He's over ninety-five years old and still fit as a fiddle, sharp as a tack. I've witnessed over a dozen times where something should have rightly killed any normal man, but not Lou." (Caleb Fisher's dialogue)
↑Vault Dweller: "It's bad enough he wants to die without you trying to kill him." Lev: "Who do you think put idea of going feral into Lou's head? Much easier to get away with it if he kills himself." (Lev's dialogue)