Two years ago, when Toronto filmmaker Matt Gallagher's daughter was born and he couldn't find work in his industry, he took a gamble on his career -- literally.

Having been introduced by friends to a subculture of poker players who make a living at the game in underground card rooms, he engrossed himself in the scene and eventually won enough money to pay his bills and provide for his family.

Now, Gallagher is revealing his journey in the documentary "Grinders," which is screening at the Hot Docs festival.

"People see that poker is this glamorous event and you see the World Series of Poker on TV and people making millions and they're travelling the world," the Windsor, Ont., native said in a recent interview.

"What I wanted to do is I wanted to show these guys who call themselves 'grinders,' who sort of grind through their daily existence just trying to make their $200 a day or $500 a day. They treat poker as a 40-hour-a-week job that they go in at 8 o'clock and check out at 3 o'clock or 4 o'clock in the morning.

"Their objective is to get the bills paid and to pay the mortgage and get diapers on the baby and all that other stuff that people in regular jobs do all the time -- but these guys happen to do it in illegal poker rooms."

The film, which is slated to air on TVO in the fall, sees Gallagher playing no-limit Texas Hold 'Em at underground clubs in Toronto.

Featured grinders in the doc include Andre, a young player who still lives with his parents; Danny, who has a family and once went to rehab for a gambling problem; and Lawrence, whose landlord closes him out of his own poker club.

"These are guys who get together and they're all strangers and they don't know each other," said Gallagher, 42, who was nominated for Gemini Awards for his docs "Vimy: Carved in Stone" and "Tyler's Barrel."

"Although the games are friendly, they're not your friends and they're there to take your money and I'm there to take their money and there's a real stiff competition that circulates around these poker rooms."

Gallagher said he was attracted to poker because "it's the one game in the casino where the house doesn't have the advantage."

But getting into the grinders' scene wasn't easy.

Since underground poker clubs are illegal, players were reluctant to go on camera and Gallagher had to promise the guys who ran the games that he would never show the exterior of their buildings.

"When I went to my first game, they actually thought I was a cop and that's not uncommon, because when you're new they're always on the lookout for undercover cops," said the writer-director.

"But I sort of hung around for a long time and then they found out I was a filmmaker, which in some cases is probably actually worse than being a cop, because a lot of these people are happy with the anonymity of that poker scene and they don't want it talked about."

"Grinders" also travels to Las Vegas for an interview with Toronto-born poker superstar Daniel Negreanu at his mansion.

His posh lifestyle is a stark contrast to the grinders' daily existence, which often includes very little sleep, poor diets and constant stress about earnings.

Gallagher said though he made enough money to manage his family expenses for several months, he also encountered a severe dry spell that eventually turned him off the scene.

"At a certain point, I thought to myself: 'I'm probably not good enough at poker to make a living at it,' so I decided to pull back that part of my life a little bit," he said.

"I still play occasionally but not like I was playing when I was making the film."

"Grinders" also documents Gallagher's emotional turmoil as he and his wife try to have a second baby.

He included the story, he said, because it mirrored what he was going through as a grinder.

"The doctors, they started to talk to us in terms of risk and probability and odds and all these terms that I was using every day in my world of poker," he said.

"That was sort of a moment where you think to yourself: 'OK, well this is very much like what we're going through, or this is very much like what the subjects in my film are going through. We're all taking chances and we all have risks that we have to sort of calculate and we all have to sort of survive."