Linda and William Mackenzie were hailed as heroes by emergency crews who said their quick actions in trying to block the flames and smoke at their front door helped save them and foster son aged five.
He was lowered out a front window to safety while they cowered inside waiting or rescuers to save them.
It was thought a plastic bottle containing a liquid and rag was deliberately set ablaze through the letter box of their front door home in Edinburgh’s Pilton Avenue at around 8.30pm on Wednesday.
Lothian and Borders Police confirmed that the blaze is being treated as wilful fire-raising.
Linda, 52, and William, 56, a salesman for Screwfix, were both treated at the scene for smoke inhalation. The boy was taken to the Royal Hospital for Sick Children in Edinburgh.
Shocked William said: “The wee man was in his bedroom, Linda and I were in the living room. I smelt burning but I thought it was coming from the loft.”
“I got two wet towels at the door and went to the wee man in his bedroom.
“The fire-fighters took him down from the front window. They then asked us to stay in the same room so I went to Linda in the living room until they came for us.
Mrs McKenzie said: “I went to the top of the stairs opened the door and could see the front door was on fire.
“I was on the phone to me sister at the time and I had to tell her, ‘I’ve got to go my house is on fire.
“I was jumping on the floor and shouting. It seemed to take ages to get us out.”
She added: “My son had been round for dinner with his partner and daughter. They left at 7.30pm
“Then we got the boy organised for the night about 8.20pm. They must have been doing it when I was putting the wee man to bed.”
The couple say they are baffled as to why this has happened and think it must be a random attack.
Mr McKenzie said: “I wouldn’t think it’s got anything to do with the fostering. I don’t think that’s possible.”
The couple have tried to keep the seriousness of the incident away from their foster son who returned to school as normal in the morning.
Mr McKenzie said: “He was quite chipper this morning. He got to have a go on the fireman’s ladder so he’s happy.
“The ambulance man also printed out his ECG and he’s taken that in to school to show his pals.”
The McKenzie’s own son, Craig, 30, an office worker said: “The thought of it is sick enough, but to actually go through with it is unbelievable.
“We left just an hour before and could have been caught up in it as well.”
Detective Constable Steven Gray of Lothian and Borders Police said: “It’s a very peculiar incident and random.
“The family are confused, as are we.
“At this time we are following lines of inquiry to establish why and who did this.
“We do not know of a motive at this time. The family are well liked and well known within the area.
“We request that anybody with information of suspicious behaviour in the area on Wednesday night report it to the police.”
Downstairs neighbours, Mr and Mrs Tait, said they were alerted to the calls of the McKenzie’s by their 14 year grandson, Owen who was staying with them
Mrs Tait, an auxiliary nurse at St Columba’s Hospice said: “Somebody was shouting and screaming on us.
“There was a bit of commotion, I could hear someone shouting but I thought it was just the kid having a tantrum.
“Willie was leaning out of the upstairs living room window, he said to John there was a fire at their door and they couldn’t get out.
“The fire-fighters were here really quickly, about three minutes.
“Before they arrived John had hit the bottle away from the letter box. He burned himself.
Another neighbour, Alan joined John with a fire extinguisher to help battle the fire.
He said: “The flames were something else. It’s a PVC door, I can only imagine the fumes that were going up to them.
“It was frightening, really frightening.
“We’ve lived here for 34 years and have never known of something like this.
“It’s scary, it’s really scary.”
Peter Ranaldi, 82, a retired fish marketer, lives opposite the flat that was attacked.
He said: “The wee dog was making a noise and when I looked through the front window, I saw the lights flashing and I thought what are the lights flashing for.”
“The fire truck with the ladder was out front and the ladder swung round to the window. I don’t know how many people were inside but I saw the fireman bring people down.
A spokeswoman from Lothian and Borders Fire and Rescue said: “The fire started in the letterbox of the upper villa flat.
“Two breathing apparatus were used and a high pressure hose reel.
“It was wilful fire-raising and a full investigation is taking place.”
They also praised the quick-thinking actions of the occupiers who used advice gained from a previous fire safety trip.
The spokeswoman added: “They placed a towel at the door at the top of the stairs to stop smoke spreading, they went to the window for ventilation and they made themselves visible to the crew on arrival.”
A police spokesman said: “We are investigating a deliberate fire-raising that happened at a property in Pilton Avenue, around 8.45pm yesterday.
“Anyone who was in the area at the time, who noticed any suspicious activity, should contact police immediately.”
