"K-9," radios Const. Glen MacKenzie of the Saanich Police Canine Section, "I'm en route to that red Mustang." A stolen car racing down the Malahat Highway on Vancouver Island has evaded police in a high-speed chase. By the time police locate the car in a Victoria suburb, the driver has vanished.

Police service dog Ace is immediately on the case - 37 kilograms of muscular black and tan German shepherd straining eagerly on his lead as he picks up the thief's scent. MacKenzie, his handler, jogs behind at the end of a ten-meter leash.

At a picnic area filled with people, Ace heads straight for the shore of Langford Lake and wades into the water. "Where are you going, buddy?" a puzzled MacKenzie asks his partner as he follows, thigh deep. Some meters out, Ace suddenly turns left and swims parallel to the shoreline.

Down shore, standing on a small dock, another officer waves his arms. "He didn't come this way!" he shouts. But Ace continues to swim towards him. Reaching the dock, he dives underneath and seconds later resurfaces - dragging the suspect with him.

MacKenzie and Ace are a potent crime-fighting team. During seven years working with MacKenzie, the dog has been directly responsible for more than 300 arrests - everyone from shoplifters to drug dealers to murderers. But most remarkable of all is the close relationship between MacKenzie and his canine sidekick. "In 24 years of police work, I've never seen anything like it," says Inspector Mike Chadwick, head of the Saanich Uniform Division. "They're so close, I swear they could finish each other's sentences."

At seven o'clock on a rainy, windy February night, I arrive at Saanich police headquarters just as MacKenzie and Ace are readying for a night shift. Ace rolls on the floor, paws in the air, shamelessly soliciting belly rubs. "Some tough police dog you are," 38-year-old MacKenzie scoffs.

Ace jumps into a large cage in the back of MacKenzie's Ford Explorer and we set off to cruise the municipality, a bedroom community for the city of Victoria. Three police radios mounted on the dashboard crackle with calls. One announces the license-plate number of a stolen red Nissan, and McKenzie adds it to his "hot sheet" list above the drivers door.

Just after 11 p.m. MacKenzie picks up the radio and mutters a few words. Ace leaps to his feet and yips excitedly. "That dog can read my mind," MacKenzie chuckles as he plants his foot on the accelerator. "They've spotted that Nissan."

First on the scene, we find the car abandoned on a front lawn, doors wide open. "Two 'runners'," MacKenzie notes. Ace is frantic with anticipation as MacKenzie slips on the dog's vest like tracking harness and clips on the lead.

Without a word from MacKenzie, Ace heads to the driver's side of the car, turns a circle and dashes off into the rainy night, head and tail down, ears forward. Ace is tracking a "scent cone," a cocktail of smells from the suspect's body, his clothing and even the grass he's trampled.

I struggle to keep up as the pair weave through a maze of backyards. Ace tracks up a driveway, raises his head and tail for an instant and looks to the right. "Thats the direction the second suspect took," MacKenzie pants. "We'll get back to him in a minute."

Ace is already inside the garage barking at a parked car. Using the abrupt German commands many handlers prefer, MacKenzie shouts, "PLATZ!" ("Get down") and the dog crouches on the spot.

"Come out of I'll send in the dog!" he yells. A teenage male crawls out from beneath the car. It has been only two minutes since we spotted the stolen Nissan.

As backup officers handcuff the suspect, MacKenzie takes Ace back to the spot where the two suspects separated. "Heavy rain washes the scent away quickly," MacKenzie says. Nevertheless, Ace picks up the track and we're off again. Soon there is tension on the leash, which tells MacKenzie the scent is getting stronger. Suddenly the dog stops and barks. MacKenzie searches with his flashlight. Five meters up a tree perches another young man. "Call off your dog," he shouts, fear in his voice.

Other incidents have not ended so peacefully. Once, MacKenzie was awakened at 3 a.m. by dispatch: An officer had pulled over an impaired driver, who then knocked her to the ground before fleeing.

At the scene, Ace tracked the suspect into a thick clump of evergreens. Following behind, MacKenzie heard a sickening thud. He rushed into the grove just as the suspect kicked the dog. Ace lunged, sank his teeth deep into the man's thigh and hauled him down screaming. Although Ace had been smashed across the shoulder with a large rock, he didn't flinch when MacKenzie carefully examined him that night. Two weeks and eight arrests later, it was discovered the dog had a broken rib.

"Ace lives for me," says MacKenzie, "and he would die for me."

Raised in Kamloops, B.C., MacKenzie joined the RCMP in 1982 at age 20. After four years with the RCMP in Alberta, the sandy-haired, blue-eyed officer moved with his young wife, Shannon, to Saanich, where he joined the municipal police force.

MacKenzie often volunteered to be the "bad guy" during police dog training and became fascinated by the intelligence of K-9s. "I want to be a dog man," he told his superior one day in 1990. MacKenzie's request was granted, and he was given German shepherds with good bloodlines to "test drive" for persistence, courage, and intelligence. But six months and 16 dogs later, MacKenzie was becoming discouraged. Finally he contacted Sgt. Doug Deacon, an instructor with the New Westminster Police Service. In February 1992, Deacon found 14-month-old Ace.

At a dog trial, MacKenzie set his stopwatch and sent Ace into a field of tall grass after a ball. If a dog searches for seven or eight minutes before giving up, it has potential. Ace searched for 40 minutes. MacKenzie knew he's found his dog.

In a test for courage, a "bad guy" runs from the dog, then turns and threatens him. Ninety-nine percent of dogs flee in fear, but Ace stood his ground. Under gunfire he didn't flinch. As for tracking skills, Ace had only to be given a scent once and he remembered. After three months training, he sailed through certification, and on June 22, 1992, MacKenzie hit the streets with his new partner.

A very real test of the dog's courage occurred in 1994. A man had fired three shots at Saanich police as they arrived at a farmhouse to answer a domestic-dispute call. An emergency-response team, along with MacKenzie and Ace, were called in. Close to 40 officers surrounded the site. For six hours the man refused to respond.

Finally, at dawn, police fired tear gas through the windows, and the suspect staggered out clad in a heavy winter coat, hands deep in his pockets. "Show your hands!" shouted the team leader. Ignoring him, the man continued towards the bushes where MacKenzie and other officers were thinly shielded by shrubbery.

MacKenzie commanded the dog to take the suspect "HAGGEMUP!" he shouted. Ace hit the suspect shoulder high and knocked him flat.

One of Ace's most famous tracks began late one day after a woman walked into her upstairs bedroom and found an intruder. For an exhausting 40 minutes after MacKenzie was called to the scene, he followed Ace over dozens of suburban fences. Suddenly the dog stopped, looked up and barked, his signal that "the bad guy is right here". MacKenzie could see nothing. "Where is he, buddy?" he asked. The dog jumped onto a rickety platform and then to the roof of a woodshed. MacKenzie scrambled up to find himself face to face with the burglar, lying flat on the roof.

Ace's tracking has proved reliable in court as well. When a repeat offender, a house burglar, was about to be acquitted because no witnesses could make a positive identification, MacKenzie stepped in to testify. He recalled how Ace had located the stolen goods in the bushes the night of the crime, then tracked the suspect down as he attempted to stroll away.

"A dog's nose is between 3,000 and 30,000 times more sensitive than our own," he explained. "While we smell our mother's stew, a dog smells carrots, potatoes, onions and meat."

Persuaded that the dog had found the right man, the judge sentenced the thief to two years.

In June 1995, MacKenzie noticed Ace walking strangely. Shepherds can have bad hips, he thought, and took the dog to the local vet Dave Kirby. After weeks of testing, Dr. Kirby called MacKenzie into his office. "I'm afraid it's degenerative myelopathy, a disease similar to multiple sclerosis," the vet said. The paralysis would move up his spine until until it paralyzed his lungs. "It's unlikely Ace could continue to work for more than a month or two. His hind legs could become paralyzed within six months."

Reluctantly MacKenzie set about training another dog. Before Ace got sick, the team had been training to go to the Canadian Police Canine Association Trials in Vancouver. Kirby advised against it. "But Ace lives to track," MacKenzie told the vet. "He'll die faster if I leave him at home."

On Labor Day, 1995, Ace's fierce concentration and sheer will won the competition over 35 other teams. But for MacKenzie the victory was bittersweet; he was sure his friend would soon be gone.

A month later, through persistent research, Kirby located Dr. R. M. Clemmons of the University of Florida, who had been working with an experimental medication that looked as though it might slow Ace's disease. They decided to try it. Miraculously, within two months Ace's paralysis seemed to stop and he was tracking like his old self again.

Off duty on June 8, 1998, MacKenzie was training Ace in an open field outside Saanich in the sweltering heat when his pager rang out: Five teenagers were robbing a home nearby. By the time he arrived, three had been arrested and two had fled. Ace took off across a field of chest-deep hay. Running flat out to keep up with the dog, MacKenzie could see the pair fleeing 500 meters ahead. MacKenzie let Ace off the leash. He leaped across a stream and pulled down one of the youths. MacKenzie had no handcuffs. "Put your hands behind your back, and don't move or the dog will get you," he warned the thief. "Stay!" he instructed Ace, then raced off towards the main road to flag down a police car.

With the first of the runners in custody, MacKenzie and Ace set off after the second. They tracked through forest and across fields for eight kilometers until they reached a golf course. Following their progress, several police cars patrolled the perimeter of the course. Suddenly Ace collapsed, panting furiously, his eyes glazed over. Heat stroke! I've got to get him to water! thought MacKenzie. "Police emergency!" he shouted to a golfer. "I need your cart!"

At the first water hole, he held the dog's head above water and Ace began to come around. A police officer shouted across the green, "We got him!" Ace's tracking had forced the suspect into the open.

Less than a month later, on July 1, MacKenzie opened the back door of his truck to send Ace on a drug search. The dog was so weak he could barely stand up.

This time Ace was diagnosed with autoimmune hemolytic anemia, a rare condition in which the body rejects and kills off red blood cells, which carry oxygen from the lungs.

Devastated, MacKenzie headed home. Around midnight Kirby phoned. "Can you find another dog for a blood transfusion? It's our last chance."

It was after 2 a.m. when MacKenzie arrived at the clinic with another dog. All night MacKenzie stayed at Ace's side, and by morning the dog's red-blood-cell count had risen slightly. "If he makes it through the next four days, we might get him back," said Kirby.

During the next two weeks, Ace's red-blood-cell count continued to rise, but he remained very weak. "Let's take him off the drugs and see what happens," Kirby advised. Within days, Ace began to improve.

For two months MacKenzie kept Ace off the job. Then, one evening in late August, the dog whined so piteously as his partner headed out on shift that MacKenzie relented. "Let's go tracking," he said, slipping on the harness. Ace worked like he'd never been away. The following morning MacKenzie told Kirby he was taking Ace with him to the Nationals the following weekend.

On September 4, without a single training session, Ace tracked and searched and apprehended "criminals" with such skill that he won the Canadian Police Canine Association Trials for the third time. "He's some kind of wonder dog," Kirby confesses. "Most dogs just don't have his kind of inner strength."

Ace's paralysis has never returned, and today Canada's top police dog continues to work at MacKenzie's side.