IT is every parent's worst nightmare.

Laura Cuthbert had left her three-year-old son Felix alone in the lounge while she grabbed something to eat from the kitchen.

When she returned minutes later, he was gone.

"My mother's instinct kicked in and I just thought 'there's something not right here'," said Mrs Cuthbert.

"Everyone was telling me to calm down but I knew something was wrong."

Mrs Cuthbert had been visiting her friend's home near Eaglesham, East Renfrewshire in August 2018. The property backed onto a small loch.

She said: "We all started running around looking for him, then there was this scream from outside - my friend shouted 'somebody call an ambulance' because she had seen him face down in the water and pulled him out.

"I ran out and I just remember holding him in my arms and screaming 'no'."

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The drama is captured in the first episode of a new ten-part BBC Scotland documentary series, 'Paramedics on Scene', which will begin airing on Sunday.

Mrs Cuthbert, 36, from Rosyth in Fife, said she remembers performing cardio-pulmonary resuscitation (CPR) on her son - something she had never done before - until the first paramedic arrived and helped her to carry Felix up the hill and cut off his wet clothes.

The situation was critical, however.

Brian Forbes, the lead paramedic on the day, said the outlook for Felix was poor.

"When we arrived the child was 'dead'. He was lifeless, he wasn't breathing, it was just absolute chaos.

"The Mum was screaming, everyone was screaming. As a paramedic, you try to block that out."

Mr Forbes, a paramedic with nearly ten years experience who now manages the Scottish Ambulance Service's special operations team, said it was one of the few cases in his career where he felt close to tears.

He said: "Felix was in the ambulance, it was just about to leave and I was speaking to the Mum. She just grabbed me and gave me a huge hug.

"I knew at that point we had done all we could, so it was quite emotional for me because of my experiences in the past of going to jobs like that - I really didn't think it was going to be a good outcome. I didn't think Felix was going to survive."

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Felix, who has autism, was rushed to the Royal Hospital for Children in Glasgow.

He had hypothermia and was immediately placed in an induced coma. Doctors also prescribed antibiotics to fight off any infection from the water in his lungs.

The following day, medics reversed the sedation to see if Felix could regain consciousness.

"After about 10, 15 minutes, Felix woke up like 'what is going on here?'," said Mrs Cuthbert. "He was trying to pull out the tubes and I just kept kissing him.

"The incident happened on Tuesday morning and by Wednesday afternoon, he was just back to himself. They had to check for brain damage, but we knew there wasn't any."

Meanwhile, Mr Forbes - who had been off-shift since the emergency - said he could not stop wondering what happened.

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Unusually, when he returned to work days later, he and a colleague decided to drop in to the RHC to find out for themselves.

"It's not something that's done all the time, but it had been playing on my mind," said Mr Forbes. "The nurse wouldn't tell us his condition, she just pointed us to a side room and said 'go in'.

"We said we didn't want to because we didn't know what to expect. It's encroaching on a family and maybe giving them a bit more stress than they need.

"But the nurse kind of forced us to go in and here was this wee boy jumping up and down on the bed.

"That was quite an emotional experience as well. I don't want to say we had him written off but we really didn't think the outcome was going to be that good or that quick.

"A little boy had gone from being clinically 'dead' to jumping up and down on a bed six days later."

The programme also covers a team of paramedics as they search for a hillwalker stranded on the Pentland hills with chest pain. The man, in his 70s, turns out to be a cancer patient recovering from treatment for stage four colon cancer.

There are also fears for a former soldier, aged 40, who has become critically ill with sepsis in less than 24 hours as a result of a throat infection, and the case of a 92-year-old woman in Edinburgh who needs to be admitted to hospital due to labyrinthitis - a disorder causing balance and gait problems - which is putting her at risk from falls at home.

Paramedics on Scene airs on BBC Scotland, Sunday September 29 at 9pm