Three American soldiers plunge into the Niagara River and swim to Canada. Deserters, refusing to return to Iraq under the U.S'.s "stop loss"? policy, they seek refugee status in Canada. Major Mike Kessler and his Immigration and Customs Security (ICS) Squad are forced to deal with the fallout - from Canadian anti-war protestors to an incensed American four-star general. One of the soldiers has a psychotic breakdown forcing Major Kessler to face his worst nightmare.

An international assassin, Monita Persaud, turns up in downtown Toronto. Her target: a political cartoonist who has enraged the Muslim world. The ICS squad, with the help of US Homeland Security Special Agent Bianca LaGarda, tracks down Persaud, only to discover a more ominous conspiracy. It's what Monita Persaud doesn't know that poses the greatest threat - to the life of one of the ICS squad.

Shipments of poisoned African heroin are hitting the streets of Toronto. Junkies start dying from the toxic drugs and ICS must race to track down the smugglers. The investigation leads them to a Kenyan flower merchant, his troubled daughter, and a mysterious English woman named Abi Mitchell. As Kessler zeroes in on the African smugglers, Mitchell gives him much more that he bargained for.

In a small village straddling the Quebec/Vermont border, a U.S. fire truck is held too long at customs, allowing a Canadian house to burn down. Long-simmering tensions erupt among the residents. Moose and Layla travel to the divided town, and are forced to deal with spurned lovers, historic feuds, and the surprising emergence of a 60s era FLQ bomb-maker.

In southern Alberta, an eco-terrorist sabotages a pumping station, and cracks the mainframe of Westech Oil. Gray and Layla travel to Calgary, where they uncover an international corporate espionage scheme to disrupt the sale of groundbreaking oil extraction technology. Layla meets, and falls for, Jimmy Kosik, a hot "environmental consultant"?, but Gray discovers that Jimmy is not who he seems.

An American pop star collapses in New York City and her passing is linked to a Canadian cancer medication, prescribed in Toronto and shipped across the border. An autopsy shows the medication to be a counterfeit. Kessler and LaGarda investigate the Canadian pharmaceutical company responsible, and its indignant CEO. Kessler discovers, LaGarda's interest in the phony drugs is much keener than she is letting on.

In southern BC, a fundamentalist Christian sect is moving teenaged girls across the border, to serve as wives for their polygamist leaders. When a young Canadian border guard disappears, Gray and Maggie dive into the complicated, passionate and highly political world of the extreme religious sect. In the process, Gray encounters Liz Carver, a stunning American DHS agent and finds her impossible to resist.

A media frenzy erupts when it's leaked that 41,000 illegal immigrants, all with deportation orders, have gone missing across Canada. As Minister Fleischer takes the heat, Kessler and his ICS squad swing into action, rounding up illegals: from Colombian drug lords to South Asian cyber-sweatshop workers. When Maggie encounters two young Filipino children, victims of human trafficking, she crosses the line, and becomes personally involved.

A former Canadian soldier, Tom Kelvin, freaks out in the customs hall at Pearson Airport. Moose tasers him, and Kelvin drops to the floor, dead. Amid the ensuing controversy, it's revealed that Kelvin was a drug mule, with a condom-full of heroin in his stomach, direct from Kandahar, Afghanistan. Kessler and Liz Carver investigate Kelvin's scheme. Is the Canadian military involved? Or the American private security firm that employed Kelvin? The answers come from a surprising source.

A Russian man is found frozen in a railway car. He turns out to be a former KGB agent with Russian mob connections. As ICS investigates, they travel from the high arctic, where African blood diamonds are being "laundered"? by Canadian mines, to an upscale New York City penthouse, where Layla encounters an old flame.

MI-6 Agent Charlotte Bates escorts a Tamil gang member to Toronto for his son's life-saving surgery. In return, the man will testify, in a British court, against a leading terrorist. The neurosurgeon set to perform the boy's operation ishuged and violence erupts in the city's Tamil community. Faced with an escalating gang war, Kessler must make an agonizing choice.

With global warming, the Arctic has become navigable, and the race to claim it heats up. As a four-nation conference on the issue unfolds in Toronto, a faraway collision under the polar ice turns a group of Canadian sailors into bargaining chips. Kessler and ICS must find a way to broker a deal that saves the sailors without selling out Canada's future in the Arctic - even if that means betraying personal bonds to U.S. Agent Carver, and British operative Charlotte Bates.

ICS discovers that toxic sludge is being trucked across the border and dumped in the Canadian wilderness. They follow a trail to a vicious criminal gang, who gain control over Gray and his father. As Gray struggles to save his father, he sets off a chain of events which bring about the season's shocking conclusion.