Rianne Murtaugh, later known as Rianne Murtaugh-Butters, is the oldest daughter and child of Roger and Trish Murtaugh and the older sister of Nick and Carrie Murtaugh. She is married to Sergeant Lee Butters of the LAPD.
Rianne was once a headstrong, slobby, selfish, teenage girl who smoked pot for a time, but still showed her love to her family. When she first met Martin Riggs, she romantically had a crush on him. It would continue for awhile while she still had other boyfriends she was dating, all the way up until she married Lee Butters. It is unknown how she got kidnapped, but it is implied she got lured into a trap, along with her boyfriend, where she would receive some pot, but instead got abducted by Mr. Joshua and Shadow Company, who murdered her boyfriend Mark. After she was rescued by Riggs and her father, she changed her habits for the better and aspired to become an actress.
Rianne appears celebrating her dad's 50th Birthday with her mom and siblings by bringing him a birthday cake while he's in the bathtub and singing to him. She then tells her dad that he should shave his beard because it's getting gray making him look old. Later that day, Rianne shows her dad her New Years Eve dress and gives him a kiss on the cheek and wishes him a happy birthday before she leaves for school with her friends, to which she also volunteers to walk her sister Carrie to school since her brother Nick and his friends left without her.
When her dad brings his new partner Martin Riggs home for dinner the next evening, Rianne is strucken by Riggs' handsomeness to which her siblings make fun of her for having feelings for Riggs to which Rianne tells them to stop it. After dinner, Rianne asks her dad if she can go out with her boyfriend Mark tomorrow night, to which her dad says no because she's grounded for smoking pot in the house, but with some help from Riggs, Rianne's dad tells her she can go on her date tomorrow night.
The next evening, Riggs and Roger get a call that a dead body was found on Roger's lawn and it matches the description of Rianne's boyfriend Mark, to which they race to Murtaugh's house and find out that the murderers of Amanda Hunsaker and her dad Michael Hunsaker, General Peter McAllister, Mr. Joshua and their men of Shadow Company have killed Mark and kidnapped Rianne. Mr. Joshua calls Roger and tells him that they have his daughter and that they wanna know about what Hunsaker told Murtaugh about them and to meet them in the desert tomorrow.
The next day, while Riggs hides in the desert grass, Roger meets Mr. Joshua and his men in the desert to which they show him Rianne. Roger tells her everything will be okay. Joshua says that Rianne will be free if Roger goes with them, but Roger orders Rianne to be set free first, even showing his weapon a hand grenade. But Joshua shoots Roger, grazing him in the clavicle, causing him to drop the grenade, which was just a smoke-screen bomb, and a fight breaks out. During the gunfight, Rianne tries to escape in the bad guys' limo, but she is caught, as are her dad and Riggs.
At Shadow Company's hideout, the men bring Rianne into the room where her dad is tied up and she asks her dad to please not let them hurt her. Gen. McAllister orders her to be hung by her hands on a pipe, to which she is. McAllister then checks Rianne out and tells Roger that his daughter is "one good lookin' young woman," to which Roger tells McAllister to not touch Rianne, but McAllister asks him to spare his life. But, before he can lay his hands on Rianne, Riggs bursts in and throws Endo's lifeless body at McAllister's men and shoots afterwards, to which McAllister escapes and Riggs sets Roger and Rianne free.
Outside, Roger identifies himself to a cop and asks him to get some backup and take care of Rianne, while he and Riggs go find and stop McAllister and Joshua, to which the cop leads Rianne to safety. In the end, after the defeat of McAllister and Joshua, Riggs goes to the Murtaugh house on Christmas and Rianne answers the door. Riggs asks her to give her dad his Christmas present from him, which is a hollow-point bullet, in which Roger would understand about. Rianne says she will and also thanks Riggs for saving her life. She asks him to come in, but he says no and leaves and wishes Rianne a merry Christmas, to which she says the same before saying bye, revealing that she still has feelings for him. Before Riggs leaves, Roger comes out and tells him to come in for Christmas dinner with them after all they've been through, to which he does and reveals to Roger that Rianne really likes him, to which Roger tells Riggs sarcastically that if he touches his daughter, he'll kill him.
In the second film, Roger tells Riggs at work that Rianne will be appearing on a commercial in the evening, to which Riggs tells everyone at the police station about it, which they all clap for her. This makes Roger mad, because he believes his daughter will not do very well, then looks at her picture on his desk and says "With this crowd, baby, you better not stink".
Later that evening, Roger, his family, Mickey McGee and Riggs gather at his house to watch Rianne's commercial. Rianne's new boyfriend George also comes over to watch the commercial and she introduces him to everyone. In the commercial, Rianne and George appear on the beach and talks to the audience about using condoms, which makes her father mad that his daughter appeared in a commercial promoting them about safe sex tips, that he shuts the TV off and tells Trish to take Nick and Carrie upstairs, and orders George to go home. Rianne apologizes to George for the date being a big blow up and tells him that she'll buy him a beer, to which Riggs says "Let him buy the beer. You're under 21". It later turns out the commercial was only the least of Roger's worries, because he knows that every one of his fellow cops watched the commercial and will be teasing him to no end with condoms.
Later that night, when Pieter Vorstedt and his men come into Roger's room and tie up and gag him and Trish with ductape, they warn Roger that he and the other officers stay off the case. Rianne, Carrie, and Nick come in after the bad guys leave and untie their parents and ask them if they're okay.
Rianne doesn't appear throughout the rest of the film after this, but according to Roger, she, Carrie, Nick and Trish all went to Trish's sister's house in Bellflower for their safety for now after the ambush. However, she is still seen on her commercial again by Leo Getz who thinks she has a great body, not knowing she's Roger's daughter. Roger turns the TV off once again, still upset that his daughter appeared in a commercial about condoms.
Rianne appears in the third film calling her house from a payphone and asking Riggs to talk to her dad to which Riggs tells her sarcastically to not call him there anymore and gives the phone to Roger to talk his daughter.
Later on, when Riggs is waiting for Roger outside a gas station, he notices Rianne being held hostage by a gunman and runs to the scene. Riggs jumps on the gunman, but quickly finds out that he is an actor with a rubber gun and that Rianne got a new job appearing in a movie. Riggs apologizes to Rianne, the gunman actor and the director for ruining the take of the movie and Rianne tries to explain to the director that Riggs just thought she was in trouble, but the director fires her anyway for no real apparent reason. Her father comes to the scene too and puts his arms around her to comfort her. Riggs tries reason with the director by slapping and punching him and makes the director to give Rianne her job back after taking the blame for the misunderstanding.
When Riggs and Roger get involved in a shooting with some gang members, and Roger kills Darryl after being shot at. The next day, Rianne shows up at Riggs' trailer and tells him that her dad didn't come home and asks him to find him for her. Riggs goes to her Roger's boat that night and finds him drunk and Roger gets mad that Rianne went to Riggs' trailer, thinking Rianne and Riggs slept together to which Riggs says no and manages to calm him down and make him get a hold of himself.
A few days later, Rianne is seen celebrating her Dad's retirement from the force with her Mom and siblings by presenting him with a cake. But Roger tells them that he isn't going to be retiring after all and Trish shoos Rianne and her siblings and Leo (who came to see Roger) out the door. In the end, Rianne kisses Riggs goodbye on the mouth and waves goodbye to her dad as she leaves for work. Roger then tells Riggs to not kiss Rianne and to shake her hand instead. But Riggs tells Roger he's already spoken for having a relationship with Lorna Cole.
In the fourth film, Riggs reveals to Roger that Rianne is pregnant with his first grandchild and this makes Roger upset because he believes that Rianne isn't married. About 9 months later, Riggs' fiance Lorna Cole (who is also pregnant) reveals to Riggs that Rianne, has secretly married LAPD Detective Sergeant Lee Butters, whom she met last year and fell in love with and got married, and that he's the father of Rianne's baby. However, she warns Riggs not to tell Roger because Rianne doesn't want him to know until after the baby is born, to which Riggs swears.
When Riggs and Lorna go over to Roger's house later, Rianne also comes over to go shopping with her mom and Lorna for their babies, to which Roger says that Rianne will have a tough time raising her baby on her own, still not under the impression that she's secretly married to Butters. Rianne assures him that she'll be okay, to which Riggs almost mentions about Butters being the father of the baby, but was constantly reminded by Lorna to keep quiet about it. She also interacts with the Hong Family that the Murtaugh's let stay with them until they're granted asylum.
The next day, Rianne, Trish, and Lorna are held hostage at the Murtaugh home by Wah Sing Ku and his henchmen while some of the men kidnap the Hongs, while Ku and some of his other men waited for Roger and Riggs to come home. When Roger and Riggs reach the house and find the girls taken hostage by Ku and his men, Roger orders Rianne and Trish to get out of the room to which they do, but are later caught again and recaptured by Ku's men and tied up, along with Riggs, Roger, and Lorna. Ku and his men sets the house on fire and leaves them to burn in the house alive. Luckily, they are rescued by one of the Hong Children, Ping, who hid and managed to avoid being kidnapped. He cuts them loose, and they all escape the burning house alive and unharmed. While Rianne, Trish, and Lorna watch sadly as the house burns, Roger and Riggs use Rianne's car to go and catch the bad guys.
They wind up crashing the car into a semi-trailer, but survive the crash and return to the house in a police car. Then, Lee Butters shows up at the house to see if everybody is okay, to which Roger introduces Butters to his family, while Roger is still unaware that Butters is Rianne's husband and the father of her baby. Before Riggs, Roger and Butters leave to go to the dental office, where Uncle Benny has an appointment, Butters whispers to Rianne to call him to which she whispers back that she will. At the dental office, while interrogating Uncle Benny, Riggs accidentally reveals to Roger that Butters is married to Rianne and is the father of her baby, to which surprises Roger, who punches Riggs for keeping it a secret from him.
In the end, Roger finally accepts Butters as his son-in-law and Rianne and Butters have a baby girl and get their picture taken with the baby, Rianne's family, Riggs and Lorna and their baby boy, Leo, and Captain Ed Murphy. It is unknown at that point what Rianne and Lee decided to name the baby and still have yet to decide.
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