In the premiere episode, Daybomber, we're introduced to Det. August Brooks, who, along with several other officers, are being over-powered by a gang of rampaging criminals with automatic weapons. Just when it looks like the worst is about to come, Det. Chase McDonald arrives on the scene, driving a black Porsche and wielding a grenade launcher. He has the situation desolved in no time, and moments later, Brooks learns that the blond hot shot is his new partner. So begins their partnership and their thrill-packed adventures.

The first episode also introduced us to the girls in the detectives' lives: Jodi, Chase's girlfriend, who works at the art gallery where Chase's metal sculptures are often displayed, and Kendra, August's wife, as well as Captain Jensen, the detectives' high-tempered superior who they continuously aggravate with their penchant for destroying vehicles, buildings, and other things during their pursuit of criminals. Det. Sam Richardson, head forensics analyst Arnold Cragmeyer, forensics assistant Annie Mason, police psyhcologist Dr. Judith Sands, and Det. Jack Lawson were among the people who assisted Chase and August from time to time on their cases.

Throughout the first season, Chase and August encountered a variety of criminals, including a gang that stole million-dollar computer chips, a deranged young man who murdered female tourists, and a man who stole human kidneys to make money on the black market. At the same time, the detectives dealt with personal issues, like the time August tried to stop a young boy from killing the gang member responsible for the death of the boy's brother, or the time the detectives worked a murder case in which the prime suspect was Chase's cousin, a mental patient.

Another personal issue for Chase was that Jodi had never been happy with Chase's job. She tried numerous times to get him to quit the force and concentrate on his sculpting. They tried to work things out, but in the end, Jodi left Los Angeles for a job with an art museum in Texas near the end of the first season.

The second season started with Chase and August trying to solve a series of grisly murders in which the victims appeared to have been attacked by a vampire, with bite marks on their necks and their bodies completely drained of blood. An unusual case for some, but for these two, just another day at work. The season continued with cases ranging from personal issues to murder and other crimes, all of which usually involved a lengthy high-speed chase and saw the destruction of numerous vehicles. Early on in the the second season (and even towards the end of the first, after Jodi left), Chase met and dated a variety of women, but none of them ever worked out.

But that all changed when he met Det. Nicole Stockman, a beautiful and tough-as-nails San Francisco detective. Escorting a key witness to Los Angeles to testify, Nicole took an instant disliking toward Chase, but the two were forced to work together after the witness escaped their custody. The witness was set to testify against crime boss Alfredo Matessa, who nearly got the man near Griffith Observatory. But Nicole and Chase came through and got the witness back, catching Matessa and saving each other's life in the process. After this, the two begin to grow more friendly with each other, dropping the early hints of a possible relationship.

Though not seen in the next few episodes, Nicole was talked about by Chase, mentioning his weekend spent up in SF with her or his (humerous) attempt to talk with her over a videophone. Returning to Los Angeles in the second-to-last episode to make a deal with Matessa for his testimony against drug lord Bobby Cole, Nicole and Chase began to discuss the possibility of her transfering to L.A. so they could be closer and start a full-time relationship. Things were looking good until Nicole decided to check up on a lead. Captured by Cole's men, she was severely beaten for information regarding Chase and August's case. When she refused to talk, Cole ordered her killed. Chase arrived just in time to see the execution, and a massive gun battle broke out between police and Cole's men.

Nicole later died at the hospital, sending Chase on a destructive path for revenge. Suspended from the force, he went against orders and purchased illegal weapons, determined to nail Cole once and for all. It all ended with a showdown on a bayside pier. Both men drew their weapons and fired. Cole was hit in the chest and died instantly, while Chase fell to the ground, clutching his stomach. August arrived in time to see his partner fall. As they waited for an ambulance, he remaked to August, "Today was a good day."