Switchman

In the premiere episode, hard-edged Detective James Ellison is surveilling the "Switchman," a dangerous serial bomber who, it is suspected, has marked a lumber mill as the next target. While alone on the lengthy, high-risk stake-out in the woods, Ellison fears he is succumbing to mental stress as he suddenly develops alarming hyper-senses. Despite the detectives best efforts, the Switchman strikes again, destroys the lumber mill in a mammoth explosion, makes a daring escape and leaves behind taunts directed at Ellison. Feeling vulnerable, Ellison chooses not to reveal his mystifying, uncontrollable hyper-senses to anyone and requests a leave of absence from the force. Ultimately, he's led to anthropology student Blair Sandburg and begrudgingly consents to let the quirky Sandburg observe him in exchange for his help in determining how to use the newfound capability to Ellison's advantage.

Before long, a beset Ellison is pursuing hunches in the serial bombing case and Sandburg is assisting him. While Ellison's former wife, Carolyn Plummer, the departments forensic expert, and his boss, Captain Simon Banks tries to figure out what's stirring with Ellison, he and his unlikely new partner begin to use Ellison's edge in the pursuit of justice.

The Siege

So the anthropologist can observe him in the field, Jim Ellison is able to get Blair Sandberg observer status with the police department. It is a baptism by fire for the unlikely new partners when The Patriots, a gun-wielding paramilitary group, take over the Cascade central police department and Sandburg winds up trapped, hiding inside the building. As Captain Banks -- whose visiting teenage son, Daniel, is among those held by the group -- begins tense negotiations to exchange hostages for prisoners, Ellison attempts to use his hyper-senses to isolate the enemy's sounds. With Banks, Jim then stealthily enters the building and thwart the take-over attempt.

The stakes get higher when an increasingly impatient Garrett Kincaid, the crazed leader of the group, launches a tow missile into a city building. Just as Ellison inches closer to a rescue, Sandburg is discovered and is used as collateral when Kincaid and his henchmen make a spectacular helicopter getaway -- with Ellison on their tail. Meanwhile Banks has to stop the remaining terrorists from escaping the building.

Killers

Ellison's sentinel-like vision enables him to identify the rooftop assassin who killed his longtime friend, an undercover police officer who had infiltrated an organized crime ring. After the detective reports his eyewitness account of the late night murder to Captain Banks, notorious hitman Tommy Juno is arrested and Assistant District Attorney Carmen Sanchez brings charges against him. When Juno presents an airtight alibi and questions how a normal human being could make a positive identification from over 200 yards away -- in the dark, Ellison is accused of manufacturing evidence.

While the trauma of the murder leaves Ellison with sporadic sensory block-out, Tommy Juno is released and Captain Banks warns Ellison to leave the thug alone. After the vengeful detective pursues the case anyway, a furious Banks takes Ellison off the streets and revokes Sandburg's access to the police department. Ellison begins to doubt himself when he prevents another assassination attempt by the same evasive hitman, Whose target is now Sanchez. In doing so, he sends Juno to the hospital. When Juno mysteriously reappears and attempts to kill Jim, we discover that Juno has died in hospital several hours before the attack. The mysterious Juno reappears again, this time holding Sanchez hostage. Ellison must battle his malfunctioning senses and the psychotic hitman in order to free Beverly, and bring Juno to justice.

The Debt

When a multiple homicide and fiery explosion at a drug lab adjacent to Sandburg's warehouse home is attributed to a bitter rivalry between two gangs, Banks asks for assistance from Lieutenant Williams and the anti-gang unit. Soon Ellison, who prefers to work alone, is paired with officer Earl Gaines, a man who grew up among gang members. While their investigative styles clash at first, Ellison and Gaines find they must protect each other as they're drawn into a vicious gang war and a corrupt cop's involvement with the dangerous drug trade.

Meanwhile, the lab explosion leaves Sandburg homeless, so Ellison agrees to let him temporarily stay at his apartment. Unbeknownst to Ellison, Sandburg moves in with a very active ape named Larry, the subject of his anthropology research. While Jim is trying to clear the wrongly accused Gaines, Larry escapes and wrecks havok on the apartment. With larry having disappeared, Blair is now free to help Jim with the case. Jim sends Blair in to protect Gaines' grandmother while he hunts down the real killers.

Cypher

After police department brass receive taunts from an elusive serial killer who adopts the identity of each victim, Ellison is assigned to the case. He is quickly prepared to make the big arrest until Sandburg, unaccustomed to undercover policework, accidentally tips the suspect off and enables a quick escape. Frustrated, Captain Banks questions Sandburg's involvement with the department. He then receives assistance from FBI forensic psychiatrist Dr. Anthony Bates, who provides invaluable insight into the killer's thought process. While Sandburg tries to redeem himself, he becomes the killer's next target.

Night Train

While suffering from the flu, Ellison takes the top secret assignment of transporting -- via train -- a police informant in the witness protection program. As the classic train winds through an isolated mountain region, Ellison battles the distorting effects a cold remedy has on his hyper-senses. Then, Carolyn Plummer and Captain Banks are tipped off that the powerful businessman standing trial in the impending arson-murder case has planned a bump-off.

While Ellison and Sandburg are distracted by their competition for the attention of Isabel Kane, an attorney escorting informant Derek Wilson, the henchmen make their move. Then, in a spectacular melee, Ellison is thrown from the train and a battle of wills begins.

Rogue

On the day Ellison is a guest lecturer in Sandburg's anthropology class, an intruder manages to steal a canister of Ebola virus from the university's nearby medical research lab. As soon as the smoke from the perpetrator's diversionaty explosion clears, it's evident that the thief is well-versed in police work, bombs and Detective Ellison's sentinel-like abilities. After he's identified as former rogue CIA agent Lee Brackett, he blackmails Ellison by threatening to unleash the Ebola virus into the atmosphere unless the detective uses his hyper-senses to help him steal an Air Force reconnaissance plane.

In an effort to ward off widespread hysteria, Ellison pleads with Dr. Sonia Price of the Centers for Disease Control, to keep the terrorist's threats quiet until he can stop him. Left with no choice but to cooperate with the crazed demands, Ellison and his guide Sandburg are forced to help Brackett cross through an intricate grid of electronically triggered mines - some active, some dormant - which surround the airplane hanger.

Love and Guns

When thugs fortified with military assault weapons pull-off a string of assaults on armored cars, Ellison's investigation leads to an international delivery service supplying rocket launchers, machine guns and automatic weapons to street gangs and organized crime. To obtain information on this crime ring's activities, he asks Sandburg to get acquainted with a fellow student, Maya Carasco, the daughter of the cartel's patriarch, Hector Carasco. The plan works well until Sandburg falls in love with her and accidentally reveals about Ellison's case. Meanwhile, Ellison is all business and only annoyed by Michelle Drennan, a beautiful, arrogant ATF agent who is assigned to work with him.

Attraction

While working the crime scenes of several recent diamond heists, Ellison is repeatedly distracted by unexplainable feelings. Then as he and Sandburg pursue a hot lead, Ellison meets the beautiful Laura McCarthy and uncharacteristically neglects the burglary assignment in favor of his overwhelming desire for her. Soon, Sandburg theorizes that pheromones have heightened Ellison's sentinel-like powers to the point of irrationally. He then becomes suspicious of the connection between his partner's uncontrollable infatuation and the strange feelings the detective experienced at the crime scenes.

Vow of Silence

When Ellison seeks a rejuvenating weekend getaway, Sandburg takes him where there is plenty peace and quiet -- an ancient monastery secluded in the mountains. Although feeling hoodwinked by Sandburg and his idea of a "New Age" retreat, Ellison is stranded with no choice but to spend one night in the austere surroundings. Then, one of the resident Monks is found murdered and the outsiders, Ellison and Sandburg, are suspected of the crime.