When six-year-old Jacob St. Jean found out that secret agents weren't just the stuff of stories, he asked his mom, Erin, to help him track down some real spies.

The pair wrote a letter to CSIS, asking if Canada's spy agency would set up a club for kids.

For four months, Jacob checked the mail daily, only to be disappointed.

"I would say, 'You know, they're spies, they're busy with important business,'" Erin told CBC News.

Then, earlier this week, Jacob received a mysterious package in the mail — and an apology for the delayed response — from the B.C. regional director of CSIS.

Canada's youngest spy

The reason it had taken CSIS authorities so long to get in touch, the letter explained, was that at first they had written to Jacob in invisible ink, but lost the piece of paper.

Jacob St. Jean

Canada's youngest secret agent: Jacob St. Jean, 6, wrote to CSIS to ask the agency to set up a spy club for kids. (CBC)

The next version had been written in code, but they realized Jacob had yet to be trained in how to decipher.

"So they finally got [around] to writing a letter in plain English and mailing it off to us," Erin said.

The letter included some tips for Jacob on how to become a spy — to be honest, loyal, smart and to listen to his parents.

And the package included everything Jacob needed to become a junior secret agent: a cap with a CSIS patch, a CSIS pin and a CSIS medallion etched with his own, unique number.

"There's a code on it," Jacob says. "Special for me ... I don't think I should tell it."

With files from Eric Rankin