A mentally unstable Singaporean woman with a history of depression and her cheating British boyfriend had a toxic relationship filled with bitter, sometimes violent rows.
And when their baby boy was born in May last year, that violence turned on him.
Doctors discovered his injuries after he was taken to a London hospital when he was six weeks old.
But the skull fracture and at least 11 rib fractures could have happened as early as 12 days after he was born.
Despite a detailed investigation, however, neither parent is likely to be taken to task as a British judge could not decide whether the infant's mother or father was to blame - both had given contradicting evidence and admitted to lying.
The judge believes, in fact, that they were colluding because both were terrified that the woman would lose the child.
"With considerable regret, I find I am unable on the evidence to determine who was the perpetrator and both parents, therefore, remain in the pool of possible perpetrators," wrote London family court judge Laura Harris in judgment grounds released last month.
This means that the baby, who is now nine months old, will remain under the supervision of a guardian until a final welfare hearing.
The rare fact-finding probe had started last December, after the local authorities of the London borough where the couple lived applied for a court order to provide for the care of the boy.
Two medical experts ruled out a fall as the cause of the baby's injuries, as his mother had initially claimed.
They said the the skull fracture had been caused by a direct blow to the head or blunt force. And they noted that breaking his ribs would have called for "significant force far in excess of normal handling, even during rough play".
The father had at one stage suggested that the rib fractures could have happened when he squeezed and hugged the child very tightly to stop him from crying. He had also admitted to smacking the baby on the head.
The father had made at least three "half-admissions" about the injuries, which the judge said she found strange.
"I am quite satisfied that neither parent has told me the whole truth. I find them both not to be reliable and truthful witnesses," she said.
The mother, while seriously emotionally unstable, was caring and committed to the baby, she noted. The father, although less patient and adept at looking after his son, seemed devoted to him. Both cannot be named to protect the child's identity.
The couple have had a stormy relationship since they first met through a dating website in 2013.
The 30-year-old woman, who lived in Singapore most of her life, had a difficult and unhappy time growing up - her father was a drunk who abused and beat her. Her mother was always at work and had no time for the children.
She, in turn, had a series of turbulent and unstable relationships - her first marriage at 24 ended when she discovered that her cheating husband had a child with another woman.
After moving to London in 2012 to work as a bank analyst, a man she met online turned out to be suffering from schizophrenia and depression, and threatened to kill himself and her with a gun which he put to her head.
Then she met her current boyfriend, who was jobless and four years her junior. A few months after their baby was born, he told her that he was involved with another woman.
He was described as immature for his age, "out of his depth" after his son was born, prone to panic attacks and anxiety, and had been warned by the police for assault.
"The coming together of these parents resulted in a relationship that was toxic," said the judge.
"To bring a new baby into this mix was likely to end in tears."
This article was first published on March 22, 2015.
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