"What happened to my baby?" The parents of Darcy Atkinson want answers about their son's suspicious death.

On December 6 of 2012, Tara Maxwell left her two-year-old son Darcy with her boyfriend of three-months, Adam Taylor.

“He was very willing to look after him,” Maxwell told 60 Minutes last night. 

Taylor had often driven Maxwell’s eldest son Gracen, now 13, to school and regularly looked after Darcy while Maxwell was at work.

That day, they had been paddle boarding at Avoca lagoon and swimming.

Darcy Atkinson died after spending the day with his mother's boyfriend. Source: 60 Minutes

It's believed that as some point the toddler hit his head and had been submerged in water for at least one second.

His mother took him to Gosford Hospital on the NSW Central Coast with bruising on his arms, legs and ears.

He had a brain injury and the stimulant Ritalin was found in his blood stream.

The following day, December 7, Darcy's father Peter Atkinson made the heart wrenching decision to turn off his son's life support.

The Deputy State Coroner described the circumstances of his death as "troubling and suspicious", but claimed there was no evidence of physical abuse.

He concluded the child died as a result of a brain injury from ingesting too much water.

Darcy 's father, Peter Atkinson, saying goodbye to his son on the day he died. Source: Facebook

Another theory, that Darcy had fallen out of bed that morning and hit his head, was also aired.

Both claims were rebuked by one of Darcy's treating doctors, Barry Wilkins, who told the inquest into his death that there was strong evidence the boy had been assaulted or "thrashed" the day before his death.

"I know that he was boxed on the ears probably that day, " Dr Wilkins said. "He died consequently."

Peter and Darcy.  Source: Facebook

Darcy's father, Peter Atkinson, remembers vividly the day he died.

"They started explaining that Darcy's eyes had dilated and they weren't able to contract or anything like that," he told 60 Minutes.

"I was hanging onto hope and I just wanted to get back into Darcy and take him and run home with him.

"When you go home after burying a child you've just got nothing to live for. They hand you a cardboard box with some ashes in it and say that's what you get out of all, everything that's happened, and you think, 'they've ripped my whole life apart and given me this bag of sand and told me to bury it'."

Darcy would have been 6 this year and excitedly preparing for Christmas at the end of his first year of primary school.

His mother still dreams about him everyday.

Darcy's mother Tara Maxwell. Source: 60 Minutes

"He cuddles me tells me hie misses me and it feels really real," Maxwell said through tears.

"It just kills me, it kills us. I'm probably going to die not knowing what happened to him."

If you have any information on what happened to Darcy on Thursday, December 6, 2012 please call Crimestoppers on: 1800 333 000.