A 10-year-old boy climbed down a 328ft (100m) ravine to reach his mother who had fallen during a mountain climb.
The family, which also included two girls, aged five and nine, ended up on very steep ground after taking a wrong turn on Ben Cruachan near Dalmally.
The mother fell and landed on a ledge with a "large drop" below, resulting in her suffering serious injuries.
An Oban Mountain Rescue Facebook post said the boy rang emergency services with his mother's phone.
He also stayed with her and kept talking to her to prevent her losing consciousness. Meanwhile, his father, whose phone is understood to have been out of charge, was looking after his two sisters.
The mountain rescue team were called out at about 19:50 on Monday. The accident had happened as the family descended the 3,694ft (1,126m) mountain.
The boy had managed to give police a description of the location and luckily the family had a torch so were reached by mountain rescue in about 30 minutes and a rescue helicopter was called in.
The mountain rescue post said: "It takes a while to deal with this sort of situation and the lady was very lucky she stopped where she did as a large drop awaited below. After her injuries were treated the best we could in the situation, she was ready to winch. All the while the lad was with his mum talking to her."
The woman was airlifted to hospital at about 23:00 while the mountain rescue team helped the rest of the family off the mountain.
The mountain rescue spokesman added: "This was a superb effort by all the Oban MRT team members and Rescue 199 in dealing with a technical rescue on steep ground in the dark. It was challenging to access, difficult medically and a challenging lift for the helicopter."
He said the boy was a "brave lad who should get an award for his actions".
"Just getting to his mum was hard, then looking after his mother in an extreme situation, talking to the police and keeping calm - he was amazing," the spokesman added.
The woman is said to be "out of danger and comfortable" in hospital.