An abandoned CN railway line cuts through the rural township of Oro-Medonte, just outside Barrie, Ont. Now a gravel hiking trail bordered by tall grass and a thin band of trees, it stretches off into the distance through farm fields almost as far as the eye can see. On a cold and rainy Sunday afternoon, a strong south wind is ripping off the last of the fall leaves. The trail is mostly deserted, but it is still the centre of a great deal of attention these days. Four Barrie police cars and a large van — a police mobile command centre — are parked where the trail intersects with a lonely rural road not far from Lake Simcoe. This is the spot where Brandon Crisp, a slight 15-year-old with dirty blond hair and green eyes, dropped his bike this past Thanksgiving Monday evening, started walking and seemingly vanished into the chilly night air.

Brandon had stormed out of his home in the east end of Barrie that afternoon, after his parents, Steve and Angelika Crisp, told him they were taking away his Xbox video game system for good. Wearing a burgundy hoodie and a light jacket, he angrily grabbed his backpack, stuffed with little more than a small blanket inside, and jumped on his bike, which he hadn't pulled out of the shed in three years. Brandon would be back, thought his parents. Perhaps cold, hungry and a little embarrassed, but he'd be back. So sure of that, Steve even called his son's bluff as he left, telling him he'd better take some warm clothes. By midnight, Brandon was still gone and the Crisps phoned the police.

Brandon had never caused his parents real trouble before. He had been a good student, and a good brother to his twin Samantha and older sister Natasha. Any disputes he did have with his parents centred on the video game Call of Duty 4: Modern Warfare, a violent, shoot-'em-up war simulation in which players act out missions as U.S. Marines or members of the British SAS. Over the past year, the Grade 10 student from St. Joseph's High School had started spending more and more time with the game and less doing typical teenage things — from basketball in the driveway to bike riding. He was once an AAA goalie, but his social circle had shrunk down to just three close friends who also played Call of Duty over the Xbox Live system, which connects players over the Internet. More than once, Angelika, a light sleeper, woke to the sound of Brandon talking to other players online in the middle of the night. They couldn't drag him away from the game, say his parents. He came home from school, put on his Xbox Live headset, and wouldn't stop playing for hours at a time. "We'd always say get off the game, go outside," says Angelika. Brandon didn't listen.

Numerous times, Steve and Angelika, concerned that their son was obsessed with the game, confiscated it for a weekend. They even tried to find a solution through compromise, once proposing that Brandon draw up a video game schedule he thought he could follow. It worked for a few days, then he was back to his old ways. When Brandon skipped school — for the first time ever — the Thursday before Thanksgiving to play Call of Duty, his parents took the game away again. When he disobeyed them and pulled the game from its hiding spot, they'd finally had enough. They told Brandon he was permanently cut off. The Xbox was taken out of the house.

What they didn't know at the time, his parents say, was just how much the game meant to their son and how troublesome that connection had become. Since his disappearance, the true extent of his involvement has become clear. While he had few friends in Barrie, his Xbox had a list of 200 people whom he played Call of Duty with online. Judged too small to keep up in hockey, the shy but competitive teenager found respect and success in the video game world, where he played on "clans," or online teams. It wasn't just a game, it was Brandon's life — something he might even make money playing in professional tournaments one day, he once told a friend. "These are the things I didn't realize," says Steve, standing in a police command centre near where Brandon vanished, his hands wrapped around a bottle of water. "When I took his Xbox away, I took away his identity."

The police are still searching the nearby fields, but the large-scale volunteer search that has been going on in recent weeks is over. Hopes that Brandon might be comfortably hiding out in one of the expensive summer homes on Lake Simcoe are all but dead. The question hangs heavier than ever: what happened to Brandon Crisp? His parents have ideas and they all centre on the video game and the growing fear that Brandon's addiction might prove fatal.