Captain Louis "Lou" Purnell Grover is a Chicago-born man who originally served as the captain of the Honolulu Police Department's SWAT team before retiring from his position for good in the aftermath of the events in the Season 4 finale episode, O ka Pili'Ohana ka 'Oi.
A 25-year veteran of the force, Grover was Born and bred in Chicago. He graduated from the Chicago Police Academy in 1989, and was promptly recruited by the FBI to go undercover in the Philadelphia Black Mafia. Upon the completion of the assignment, he returned to the Chicago Police Department. He left Chicago around 2012 or 2013, after an incident where he blamed himself for having failed to save a boy who was taken hostage by his father, which ultimately resulted in a murder-suicide. Despite Grover's best efforts, the man ended up killing his son and then himself. 
Grover made his first appearance in Aloha ke kahi I ke kahi where he and his SWAT responded to the hostage crisis inside Iolani Palace, the headquarters of the Hawaii Five-0 Task Force. He later became an enemy of Five-0's leader, Lieutenant Commander Steve McGarrett who was attempting to free members of the National Liberation Movement due to the fact that the NLM's leader had taken Steve's girlfriend Lieutenant Catherine Rollins hostage.
Grover filed a complaint against Steve with the governor. However, in the episode Akanahe, Governor Samuel Denning ordered Steve and Grover to work together to bring a summons for Ian Wright and deliver him to the courthouse. However, the situation turned into a kidnapping, and eventually to Grover and Steve having to release Ian when he hacked into the plane, threatening to crash unless he was released. The Governor later commended both the men, saying they made the right decision.
In the episode O kela me keia manawa, Steve found out that his suspect in a case, Jack Anderson, was a friend of Grover's, and let him be a part of the case to track down Jack. Eventually, they found out Jack was actually a wanted man, and Steve and Grover headed to the forest to find him. Though held at gunpoint by Jack, Grover was able to overpower him when Steve created a distraction.
In O ka Pili'Ohana ka 'Oi (episode), hacker Ian Wright returned, targeting Grover's daughter, Samantha. He kidnapped her and made Grover steal $100 million worth of drug money that Five-0 was helping to transport to aid Third World countries. He and Ian's men end up taking the Five-0 team hostage, but they were surprised when the money is missing. Grover killed Ian's men when they tried to kill the Five-0 team, and Grover finally admitted to Steve that Ian Wright had Samantha.
Steve and the team helped Grover track the money to the DOD agent who originally provided the money and a local gang who was helping him transport the money. Before they could hand over the money, though, Grover got a call that Samantha came to HPD headquarters, and said that Ian is dead after Wo Fat shot him and freed Samantha.
Though the money was recovered, Grover was forced into early retirement as a result of the incident. However, Steve offered Grover a place on the Five-0 team.
Despite being reluctant at first, Grover eventually accepted, which resulted in him becoming the newest member of the Hawaii Five-0 Task Force team and overall the fifth and final member of the team.
In the Season 5 premiere episode, A'ohe kahi e pe'e ai, Grover worked his first ever case as a member of the Five-0 team and was even seen wearing his own version of the team's tac vest.
In Ina Paha, Grover meets Sang Min for the first time. In the alternate reality, he is seen arguing with Duke Lukela about his golf clubs being stolen, only to be later interrupted by Steve's arrival.
In Season 6 episode 19, Grover and his family have to go on the run because of a case he went on in '89. On the case Lou, fresh out of the academy, is sent undercover in Philly, to take down the black mob. He does and the leader Barnes and his son Barnes Jr. are put in jail. His handler Agent Zaglar, talks to him outside of the restaurant him and Steve are eating at. After talking to his handler, he and his family go on the run. At the end of the episode, Lou and his family are found in the woods by Steve.
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As the head of HPD's SWAT division, Grover originally had little or no patience for the Hawaii Five-0 Team, believing that they often went too far and that they needed to follow the law.
He regularly clashed with Steve McGarrett, the two men often coming close to butting heads due to the fact that they had completely separate ideas of how to do things.
By the end of Akanahe, Grover and Steve had developed a strong, almost grudging respect for each other although they still remained hostile towards one another.
While the two have formed a strong bond, in Pale'la, Grover told Steve the real reason he left Chicago was the result of a murder-suicide involving a father and his child. That trust grew between them when Steve revealed in the next episode, about Freddie Hart and his death. Still, Lou still likes to make fun at Steve's expense, like when he caught a large fish that McGarrett failed to do on his first try at Spearfishing and insisted that Chin takes a picture and send it to Steve to annoy him.
Lou also has a witty and sarcastic sense of humor, often spouting some of the best one-liners in the series.
- Put his old friend Clay Maxwell behind bars on multiple charges, including the murder of his wife. 
- Carries a Kimber Warrior as his own personal sidearm with the weapon sometimes being fitted with a Streamlight TLR-2 weapon light.
- The character was named after a Captain Grover (Scott Brady) from the original series.
|Aloha ke kahi I ke kahi||A'ale Ma'a Wau||Ka 'oia'i'o ma loko||A ia la aku||Kupu'eu||Kupouli 'la||Ua Nalohia||Akanahe||Ha'uoli La Ho'omoaika'i||Ho'onani Makuakane||Pukana|
|O kela me keia manawa||Hana Lokomaika'i||Na Hala a ka makua||Pale'la||Hoku Welowelo||Ma lalo o ka ili||Ho'i Hou||Ku I Ka Pili Koko||Pe'epe'e Kanaka||Makani 'Olu a Holo Malie||O ka Pili'Ohana ka 'Oi|
|The Skin Has Been Hurt by the Point of the Spear||Knocked Flat by the Wind; Sudden Disaster||Passing Time Obscures the Past||Tiny is the Flower, Yet it Scents the Grasses Around It||Don't Blame Ghosts and Spirits for One's Troubles; a Human is Responsible||All Knowledge is Not Learned in Just One School||DNA||That Way and This Way Shifts the Sand of Punahoa||The Trunkless Tree of Kahilikolo||You and Me, It Is Hidden||To Return Evil for Evil||Where Were You When the Rain was Pouring?||The Rat was Caught Right in the Nest|
|There Was a Lull, and then The Wind Began to Blow About||Yours is the Mouth of an Octopus||Man is a Slave of Love||Like a Whirlwind, Whirling the Dust Upward||Lost in the Sea Sprays||Home Go the Very Tough Lads of the Hills||A Gripping Cuttlefish||He Cannot be Caught for He is an Ulua Fish of the Deep Ocean||Goodbye|
|Hawaii Five-0 Characters|
|Final||Steve McGarrett • Danny Williams • Adam Noshimuri • Tani Rey • Junior Reigns • Lou Grover • Kamekona Tupuola • Duke Lukela • Noelani Cunha • Quinn Liu|
|Former||Chin Ho Kelly • Kono Kalakaua • Max Bergman • Catherine Rollins • Jerry Ortega|
|Other||Lori Weston • Mary McGarrett • Grace Williams • Charles Williams • Jenna Kaye • Dr. Malia Waincroft|