He served as a Green Beret in the Vietnam War. Subsequently, he became the sheriff of Twin Peaks, a position previously held by his father and later by Harry when Frank left Twin Peaks for western Washington, where he held a long career in law enforcement.
In 2016, following Frank's retirement, his brother was diagnosed with cancer. While Harry sought treatment in Seattle, Frank agreed to return as the sheriff of Twin Peaks, having arranged to hold the position for two years, after which time, Hawk would be promoted.
After a fishing trip, Frank went to the sheriff's station after speaking with Lucy Brennan on a cell phone, which scared her, causing her to fall back in her chair. He then got an update from Maggie and the fellow deputies on situations that had occurred in the town while he was away, including a drug overdose by Denny Craig. He saw Deputy Bobby Briggs in the hallway and surmised that Denny's overdose was from Chinese designer drugs and told Bobby to keep on the lookout.
Truman then met with Hawk, concerning a message from Margaret Lanterman's log that related to FBI Special Agent Dale Cooper, who had disappeared from the town 25 years prior. He dismissed the skeptical Deputy Chad Broxford and Bobby revealed to them that Cooper was the last one to have seen his father alive, but did not know what the two discussed. Andy and Lucy's son, Wally Brando then arrived and paid his respects to Frank's brother, hoping for him to overcome his illness.
Sometime later, after a phone call with his brother, Frank's wife came to him, clearly frustrated about various things, including a leaky pipe at their house and her father's car.
Doris later returned, frustrated with Frank due to her belief that her father's car had still not been repaired.
Hawk brought pages to Frank that were found in a bathroom stall door at the station. The pages belonged to a diary belonging to Laura Palmer and recounted a dream she had where Annie Blackburn told her that the "Good Dale" was in the Lodge, but could not leave. The two agreed to fill in Harry on the details, since he was the first person to see Cooper upon his exit from the Lodge. However, Frank allowed his brother—whose illness apparently worsened—to rest before being told of the discovery.
Frank then contacted Doctor Will Hayward, who saw to Cooper's condition after his exit from the Lodge. He noted to Truman strange behavior from Cooper, as well as a possible visit to Audrey Horne in an intensive care unit, where she was in a coma.
Along with Hawk and Bobby, Frank visited Bobby's mother, Betty, who told them that she had been expecting this meeting after her husband told her about it prior to his death. She gave them a metallic container that Garland had hidden inside of a chair.
They took the container back to the sheriff's station and kicked Chad out of the conference room to open it. However, Frank and Hawk could not and an amused Bobby took them outside to open it, revealing slips of paper referring to the "Jack Rabbit's Palace" – an imaginary place where Bobby and Garland used to play during the former's childhood – and a series of letters and numbers, "COOPER / COOPER" being among them.
Frank and Hawk later discussed their destination and Hawk explained an ancient map to him. He questioned a symbol on the map, which Hawk told him that he did not wish to know about. Deputy Holcomb then came to ask Frank if he wanted to see his new car.
Truman later went to inform Benjamin Horne that his grandson, Richard, was the perpetrator in a hit-and-run incident that killed a young boy and the assault of Miriam Sullivan. Ben said he would take care of Miriam's situation and gave Frank a key to give to Harry as a keepsake, as it was the key Dale Cooper used for his hotel room at the Great Northern.
After arresting problematic Deputy Broxford, Bobby led Frank, Hawk, and Andy to Jack Rabbit's Palace, following Major Briggs' instructions. They encountered a nude, eyeless woman, who Andy noted to be important and to be kept under their care. Frank and Hawk admitted that they did not recall anything between finding the woman and Andy telling them about her.
Later, as Frank sat alone in the conference room, Hawk called Bobby, Andy, and Lucy to join then, announcing the death of Margaret Lanterman.
Andy later introduced Cooper's doppelganger – who was posing as the original Cooper – to Frank. Truman took the doppelganger to his office and was told he was visiting to take care of "unfinished business." However, Frank then received a call from the original Cooper, who had just arrived in Twin Peaks. After a brief silence, the men drew their guns on each other, but before either could open fire, Lucy shot the doppelganger, commenting that she now knew how cell phones worked.
Cooper advised Frank to stay away from the doppelganger's body and soon arrived as the room darkened and bearded men attempted to revive the doppelganger. BOB was released from the doppelganger's body and defeated by Freddie Sykes, who had been brought from the holding cells to the office by Andy.
Behind the scenes
Frank is played by Robert Forster, who had been the first choice to play Frank's brother, Harry S. Truman. The character was added to Twin Peaks: The Return after Harry's actor Michael Ontkean declined to return.
- The Secret History of Twin Peaks
- Twin Peaks: The Final Dossier
- Twin Peaks – "Part 6"
- Twin Peaks – "Part 4"
- Twin Peaks – "Part 5"
- Twin Peaks – "Part 7"
- Twin Peaks – "Part 9"
- Twin Peaks – "Part 11"
- Twin Peaks – "Part 12"
- Twin Peaks – "Part 14"
- Twin Peaks – "Part 15"
- Twin Peaks – "Part 17"
- Secrets from Another Place: Creating Twin Peaks