A heavily pregnant woman and her soldier husband were savaged by two large dogs as they tried to defend their pet Chihuahuas.
Emily Vickery, 23, and Sam Myford say they were left covered in blood after the attack at the Westbury White Horse monument in Wiltshire.
Both were treated in hospital for multiple bite wounds, and there were fears she had entered premature labour.
The owner of the bull mastiff-type dogs drove off without leaving her details.
Police say they are looking for a woman in a green Mini over the "extremely terrifying" attack.
'Cowards who watched'
The council worker, who is 37 weeks pregnant, was walking with her 27-year-old husband and their two dogs at about 19:00 on Tuesday when it happened.
Emily's sister Alice Withers said: "Emily and Sam picked up their two dogs to protect them, but they were attacked and bitten all over.
"There was a tug of war going on with one of their dogs," she said.
"Emily was bitten all over her hands, legs and bum, and was pushed over at one point."
She said the ordeal could have been worse had it not been for "our hero" Kim O'Mally, from Trowbridge, who came to the couple's rescue.
Ms Withers said that although 30 to 40 people were in the area, no-one else came to help, "despite Emily's screams".
But Mr O'Mally managed to get them inside his vehicle, although she said the dogs "were still jumping up at the car windows trying to get at them".
She added: "I'm hoping the cowards who watched it all come forward now.
"They are both really shaken up, they were both covered in blood."
The couple's Chihuahuas were also injured, with one needing an emergency operation.
PC Matt Fry from Wiltshire Police said: "The dogs are described as being large, muscular in appearance, with short, tan-coloured fur. Neither had a collar on."
He described their owner as being aged in her late 60s, wearing glasses, a black jacket, black leggings and brown boots.