Had Todd Manning use his (Flynn's) identity.
Tried to force Natalie to forfeit a pool tournament
Held Natalie and Jessica hostage.
Kidnapped Cristian Vega
Killed Cristian (That was later revealed to be a lie)
Sold Cristian into slavery to a group of drug runners.
Tried to kill Todd and Blair.
Walker Flynn is the brother of Mitch Laurence, an evil cult leader that married Natalie and turned out to be Jessica's biological father.
Walker Flynn was first seen meeting up with Todd in Atlantic City. They discussed the deal they made wherein Todd was to pose as Walker Laurence. When Blair managed to sneak up to Flynn's suite, she saw Flynn and assumed he was "Walker." She was surprised by the way Flynn was dressed as well as the fact that he was running a casino. Assuming that "Walker" and Flynn are the same person, Blair confronted "Walker" who said that he was going to leave his casino management career behind and focus on a future with her.
Kevin Buchanan had begun trying to dig up information on Walker Laurence. His P.I., Elyssa Collins, later found out that the real Walker Laurence lived in Atlantic City.
Flynn later held Todd at gunpoint, but Todd had incriminating information on Flynn which would be sent to law enforcement agencies in the event that he dies. Flynn fled to Las Vegas, warning Todd to control Blair, Elyssa, and Kevin. Todd does drug Elyssa afterwards.
A while later, a man named John McBain arrived in Llanview looking for Natalie, who was entered into a pool tournament in Philadelphia. He spotted "Walker" and sat down with him. John, who also knew of Todd's masquerade at the time, told him that Flynn had business in Vegas. John later informed Flynn that he'd seen Todd.
Elyssa gave Kevin a file as well as some photos that she took of Flynn. Kevin was confused because he'd never seen "Walker" wearing such expensive clothes. Kevin then told Elyssa that her services were no longer needed and gave Blair the information that Elyssa collected. Blair read the file and looked at a photo of Flynn, who she believed was "Walker." The photo was taken a few days earlier. Blair was angry at the fact that "Walker" lied to her. "Walker" told her that most of the info in the file was made up, and he and Blair burned the file.
Blair tried to call a number in Las Vegas. When Flynn answered, she thought he was "Walker" and was furious. Kevin later told Blair that he just saw "Walker" at the airport. Blair made plans to head for Vegas.
John reported to Flynn that he'd entered Natalie a pool tournament in Vegas. Todd tried to call Flynn and warn him that Blair was on her way to confront him. Blair unleashes her anger towards "Walker" at Flynn, who brushes her off and stated that he didn't know her and that was only the second time that they met. Todd then arrived on the scene. He told Blair who Flynn was, but did not tell her that Flynn is the real Walker. He instead told Blair that "Flynn Laurence" was his twin brother. He told Blair that they lied to her to protect her. Blair apologized to Flynn and left.
Flynn then told Todd to bring him $500,000 or he would reveal his idenity to Blair. Todd was able to get the money from Dorian. He then asked Starr to keep Blair from going to Vegas. Starr held Blair off for a while by faking illness, which did not work for long. Blair tried to call Flynn to ask him what was going on, but he hung up on her. As soon as Todd arrived in Vegas, Starr warned him that Blair was on her way.
In Las Vegas, Flynn was sure that Natalie would throw the tournament after being pressured by John. Natalie won the tournament, however. Flynn then ordered John to kidnap Natalie and bring her to his suite. When John was taking Natalie away, he ordered two men to "make the move," but they could not quite understand him. Jessica ended up following John and Natalie to Flynn's suite.
Jessica tried to get into Flynn's suite, but was captured by Arthur "Rack 'Em" Ross, a legendary pool player who was helping Natalie, as well as working for Flynn. Flynn was angry that he lost $500,000 dollars. Natalie told him that she won the tournament for herself and her family, but was promptly slapped by Flynn. Arthur brought Jessica in, and both she and Natalie assumed Flynn was "Walker." Flynn revealed himself to Natalie and Jessica and ordered John to kill them. Arthur went outside and had a face-off with Walker/Todd who arrived to give Flynn the money he demanded. "Walker" left after Cristian attacked Arthur from behind. Antonio burst on the scene with his gun drawn on Flynn. John then turned on Flynn, revealing himself to be an FBI agent. Natalie was then angry at John for using her to get to Flynn. Cristian then ran in, distracting everyone long enough for Flynn to grab Natalie and take her hostage. Flynn shot John and fled. Walker/Todd returned and Antonio attacked him, thinking he was Flynn. Jessica vouched for Walker/Todd who then told Blair what happened. Blair and Jessica went back to Llanview to try to find the money for the ransom.
Flynn had taken Natalie to a cabin. He received a call and believed that Cristian, John, and Walker were dead. However, that was a set up. Cristian, John, and FBI agents surrounded the cabin and sent Arthur to tell Flynn that the ransom money was outside. Cristian however, barged into the cabin with the money. He gave it to Flynn, and then attacked him. Flynn ended up taking Cristian hostage and left in a van. Later, John informed everyone that the van Flynn was driving went into a lake, and that both Flynn and Cristian were killed.
Back in Llanview, Flynn showed up at Todd's penthouse. Starr believed that Flynn was Todd and gave him the combination for the safe. He opened the safe and took a briefcase he believed contained Natalie's ransom money, but it was empty. Todd then decided to meet with Flynn later to turn over the money.
A while later, Walker/Todd had given Viki a ride, and Flynn managed to sneak into the penthouse "disguised as Walker." Blair returned home and did not notice the difference. Flynn then took Blair captive and said he would kill her and Walker and then "assume Walker's life." Meanwhile, Walker/Todd was also planning to kill Flynn by rigging the penthouse elevator to fall when he pressed a remote.
Flynn told Blair that Cristian saved him from drowning in the lake, and then he mercilessly killed him. Walker/Todd arrived and knocked out Flynn as he was about to tell Blair the truth. When Flynn woke up, Walker/Todd forced him into the elevator. When John and Antonio showed up, they did not recognize either man. The elevator then fell to the ground floor. When John and Antonio opened the door, they found one dead body in the crashed elevator. The survivor staggered in, with a gunshot would. After some initial confusion, and Blair accidentally revealing that Kevin kissed her, Blair knew that the survivor was Walker/Todd after his angry reaction, and that Flynn was the one who died.
Approximately a year later, Cristian Vega returned to Llanview, alive. Apparently, Flynn did not really kill Cristian. Flynn was under orders from Tico Santi, Antonio's brother and Cristian's cousin, to kill Cristian because Tico did not want any of his relatives to threaten his claim to the Santi family organization. Flynn, however, double-crossed Tico by selling Cristian into slavery to some Romanian drug-runners. The drug-runners needed someone who could speak Spanish to act as a translator for them, so Flynn gave them Cristian so he could make twice as much money for killing and selling Cristian. When Cristian explained his story to Natalie, he said that Flynn actually saved his life.