It's every parent's worst nightmare.

Jim Clark arrived home Friday in Spring Lake, west of Edmonton, to find a STARS air ambulance landing on his lawn and an ambulance in his driveway.

But it wasn't a family member paramedics were working vigorously to revive. His son's girlfriend had passed out an hour before and stopped breathing.

It wasn't until paramedics figured out that she had overdosed that they could revive her, Clark told Edmonton AM's Mark Connolly.

'Fentanyl Kills' Edmonton Catholic Schools is hosting a parent night called 'Fentanyl Kills' tonight at 7 p.m. at St. Anthony Meeting Centre 10425 - 84 Ave. Edmonton police will illustrate the dangers of fentanyl and what parents should be aware of. The event will also be livestreamed.

Clark is telling the story to alert parents to the dangers of the deadly drug, a synthetic opiate up to 100 times more powerful than morphine.

Clark said his 28-year-old son, who lives in a basement apartment, and his son's 22-year-old girlfriend spent most of Thursday night watching movies.

Everything was fine until the couple went out for coffee the next morning.

"We believe that she took the fentanyl when he went in the store, because it's a very fast-acting drug," Clark said.

The two returned to the home and were in the backyard when the woman complained of being tired, then passed out and stopped breathing.

Call 911 — she's dying

"My son yells to his mother, 'Jessica's dying,' " Clark said. " 'Call 911 — she's dying.' "

The 911 operator instructed Clark's son how to perform CPR, which he continued until EMS arrived about 15 minutes later.

Paramedics worked on the woman for 45 minutes, calling in STARS for an emergency airlift.

"I arrived home just as helicopter got there," Clark said. "As I ran up the driveway — that's when they revived her."

At Edmonton's Misericordia Hospital the woman admitted she had taken fentanyl.

Doctors told the family she should have been dead, let alone survive without any lasting effects.

"Amazing," Clark said. "It's a miracle. She doesn't have any brain damage."

But doctors told the family at least 15 other young people weren't as lucky, all dying from fentanyl overdoses at the hospital in previous months.

"That just struck me," Clark said. "We got to get this out there.

"I had never heard of fentanyl before. A 100 times more powerful than morphine; 50 times more powerful than heroin. I can't even imagine that."

Clark said he doesn't want people judging his son's girlfriend.

"She made a mistake. Hopefully, she learns from the mistake," he said. "This is a one-mistake drug. You take it once, you're dead."

Clark is pleading for parents and other adults to become involved and alert young people to the danger of such drugs.

"Why are kids taking these drugs? What's missing in their lives?"