The Legend of the Star

 is a quest in Fallout: New Vegas.

Quick walkthrough
Collect 50 Sunset Sarsaparilla star bottle caps and deposit them in the machine in Sunset Sarsaparilla Headquarters.

Once you collect enough, another collector will come to assassinate you. You can kill him and take his 8 star caps.

Detailed walkthrough
In order to complete this quest you need to find 50 Sunset Sarsaparilla Blue-star Caps and return them to Festus. Festus is located inside the Sunset Sarsaparilla headquarters, which is south of The Thorn and east of Jacobstown. Upon completing or failing this quest it unlocks another quest.

Once you give Festus 50 Sunset Sarsaparilla Blue-Star Caps, he will tell you the story about the drink. After he is done it will say quest failed, but it gives you another quest: A Valuable Lesson.

Blue Star bottle cap locations:
 * Brooks Tumbleweed Ranch - Next to the fire extinguisher on the first floor corner storage room with the stove
 * Horowitz Farmstead - On left wooden crate near the sack and two ammo boxes inside broken barn
 * Silver Peak Mine - Inside mine shack, on the table in front of/right of the entrance
 * Jacobstown - Northern Exterior Chalet, on table with cards and whiskey bottle
 * Brewer's Beer Bootlegging - Top of small bookcase, left of door to cellar
 * Bonnie Springs - In small wooden crate on earth mound, south porch of the corner of the second building away from the Campfire
 * Vault 19 - Living Quarters, Blue Sector, inside second dorm on the desk.
 * Crimson Caravan Company - Main Office, on the corner desk on top of Ham Radio amplifier
 * Gun Runners - Opposite the reception desk, on a small crate on the floor by the metal table
 * El Rey Motel - The first door on the left on the top floor leads to the room with the cap
 * Camp McCarran - By Sergeant Contreras in his supply shack near him
 * NCR Sharecropper Farms - Northeast Barracks by silos on table across from the bunk beds
 * Aerotech Office Park - Aerotech Suite 300, in the far end kitchen room
 * Vault 3 - Recreation Area, South Dorm #2
 * New Vegas Steel - On desk across the Vending Machine in the office overlooking the smelting chamber
 * Allied Technologies Offices - On concrete cubicle desk with other caps in the filing room to the right of the entrance
 * Grub n' Gulp Rest Stop - On picnic table by the shack, on top of a plate
 * Hunter's Farm
 * Kitchen work surface in pile of other caps
 * On the edge of the pile of caps
 * REPCONN Headquarters
 * Ground Floor, in the gift shop on the long cash register counter
 * Ground Floor, Robot Recharge and Security Office on the desk with terminal by the filing cabinets
 * Repconn 2nd Floor Office, East Office, across from the desk with the Red Key Card
 * Repconn Office Top Floor, Piers Isley's Office on the scattered caps pile
 * Repconn Office Top Floor, Leonard Steeple's Office, on large executive desk near terminal
 * Hostetler House - West of the Caravan, inside the house on a small table between two sofas
 * The Gray - Upper Floor, 9 o'clock room on small table with bottle on it
 * Cerulean Robotics - On the dining table close to three open fridges
 * Nellis Hangars - Mess Hall Hangar, on the two closest tables to the kitchen, a cap on each table by other caps.
 * Fields' Shack - Next to two bottles in the open fridge on the right as you walk in
 * Gypsum Train Yard - Inside the office building, back room, corner desk with burned out terminal
 * Cap Counterfeiting Shack - Table near vending machines near the caps and bottles
 * Bitter Springs Recreation Area - Right of the dead tree, on sideboard with the bottles
 * Fisherman's Pride Shack - On table left of fridge with other caps
 * Callville Bay - Captain Dean's Boat and Bait Shack - One is on smashed counter, fifth from the left wall; another on the far right corner on desk by first aid box on the wall
 * Camp Golf - House Resort, (Upper) Right Corridor Bedroom #1, on the dresser with other caps
 * Guardian Peak - Close to the cave mouth, on upturned crate by the radio
 * Mountain Shadows Campground - Main Camp next to campfire on red picnic table
 * Scavenger Platform - Northeast floating shack, on meal shelf adjacent to the ammo box
 * Boulder City - Big Horn Saloon, on large round table near entrance
 * Sunken Sarsaparilla Supplies - Across Lake Mead on the southwest side, underwater on the back end of the container
 * Goodsprings
 * Ranch House northeast of Doc Mitchell's on a table in the master bedroom
 * Ranch House east of Schoolhouse, on kitchen sideboard bar right next to an exit door
 * Sloan - Jas Wilkin's Mess Hall, on round table with lanterns and bottles
 * The Devil's Gullet - Bottom of the Gullet, in the small wooden crate next to rusty ammo box
 * Jean Sky Diving - Inside shack, on the desk
 * Lone Wolf Radio - With the other scattered caps, near the footlocker and mattress, in the trailer
 * Primm
 * Southeast ranch house on the street south of Mojave express. On top of the bookcase with the radio on it, in the living room of the shack
 * Bison street hotel: on the side table with the bottle by the sofa, in the large lobby room with the rug
 * California Sunset Drive-in
 * On the slab of concrete, by the ruined north concrete hut, right of the trash can between to bottles
 * Next to the forth bottle from left to right, on the slab of concrete, by the ruined north concrete hut, next to the trash can
 * Mesquite Mountains Crater - On the formica table next to the bottle, in the kitchen inside Hells Motel
 * The Prospector's Den - In the den building, first room to the right, on the chessboard, resting on the sideboard bar with the radio on it, near the bed
 * Mesquite Mountains Campsite - On top of the metal box, inside the northeast tent near the sleeping mattress
 * Nipton Road Reststop - On the cash register counter, with three other caps
 * Nevada Highway Patrol Station - By the body near the green cat in the cell room with the mantis nymphs
 * Mojave Outpost - Barracks: on the long section of the bar counter as you walk in, by a bottle
 * Nipton - Ranch house opposite the Trading Post general store: on top the ruined book case near the chessboard and a bottle, in the master bedroom
 * Mesquite Mountains Lean-to - Inside the tipped wooden sunset crate, between the mattress and half buried metal box
 * Junction 15 Railway Station - On the corner of the green bench, left of the boarder up door, on the platform
 * 188 Trading Post - On the wooden bar shelf, by the bottle and lantern, at the end of the blue shack bar
 * El Dorado Substation - On the trash can next to the eat o matic 3000. left corner as you enter
 * Black Mountain - Inside Tabitha's store shack, on the bottom shelf, between the two bottle crates, just behind and left of the super mutant dummy
 * Gibson Scrapyard - Corner of the low metal shelf with the tires and vehicle rims, in the main garage
 * NCR Correctional Facility - Next to the bottle on the curved desk, in the visitor center
 * Novac
 * On the small round table in the corner of the galley kitchen, in the ranch house, one building south of the No Bark Noonans Shack, northwest part of town
 * Daisy Whitmans Dino Dee Lite rental room, top floor above the far steps. On the table with the noodles and broken tv
 * Emergency Service Railyard - On the mattress on the train platform, with the other scattered caps
 * Harper's Shack - On the small table with the fan on it, near the small crate of bottles and a pressure cooker, across from the bunk bed, left room
 * Highway 95 Viper's Encampment - Next to two other caps on one of the two makeshift bedding rolls, northeastern lean-to
 * Wrecked Highwayman - Among the debris and footlocker, in the open trunk of the crashed car
 * Snyder Prospector Camp - On the top of the two ruined books, next to the bedding and sandbags under the lean-to
 * Viper Gang Ambush - On the half buried crate spilling out of the back corner of the container, east of Nipton
 * El Dorado Gas & Service - On the cash register counter with two other caps
 * Camp Forlorn Hope - Mess hall south of stream: by the bottle the table with the coffee pot, close to the metal shelves, in front of the entrance
 * Southern Nevada Wind Farm - On the metal work table with other caps, near the copy of Dean's Electronics
 * Cliffside Prospector Camp - On the chessboard with the bottle on it, on top of the damage crate
 * Searchlight North Gold Mine - On the wooden crate by the metal shelving, across from the mine cart, in the rock alcove, halfway down the right tunnel.
 * Coyote Mines - On the middle table, lower area right of the stairs, just inside the large miners shack
 * Raided Farmstead - In the open fridge with the caps and bottles, near the ammo box, inside the long trailer
 * Camp Searchlight - Fire Station, upper floor, on a dining table with two bottles, in the kitchen area, far end of the corridor
 * Sniper's nest - On the long plank of wood next to the mattress, next to the .308 ammo box, inside the lean-to
 * Cottonwood Cove - Inside the ladies restroom building on the lowest shelf with a bottle, right corner
 * Bradleys shack - Behind the sandbags, near the other caps, by the ammo box and mattress, under the wooden canopy
 * Old Nuclear Test Site - Inside the shack on the table with the science experiment and two bottles on it
 * Matthews Animal Husbandry Farm - On a wooden crate with two bottles and a cap, on the top balcony, in the western of the two ruined barns
 * Smith Mesa Prospector Camp - On the concrete block, at the back of the rock alcove, behind the lean-to
 * Blue Paradise Vacation Rentals
 * Floating above the sideboard near the mattress, with a teddy bear, bottles and other caps. in the submerged north bungalow
 * Among the floating bottles and caps near the open fridge, in the submerged middle rental bungalow