PLAISTOW, N.H. (WHDH) -- Authorities looking for a Plaistow, New Hampshire couple suspected of inflicting burns and bruises on a 3-year-old boy have upgraded charges against them to assault.

The boy’s grandmother is begging his mother and his mother’s boyfriend to turn themselves in.

“I am so mad at what they did to my baby,” said Helen Nicholson, the boy’s grandmother.

Nicholson can’t believe anyone would hurt her 3-year-old grandson, James.

“What you did to my baby is unbelievable. You almost killed him,” Nicholson said.

Last week, the boy's mother, 23-year-old Jessica Linscott, and her boyfriend, 27-year-old Roland Dow, brought James to Exeter Hospital with significant head injuries. The boy was later taken to Children's Hospital at Dartmouth in Lebanon, where he is recovering after surgery.

The couple told police over the phone the injuries were self-inflicted, but doctors rejected that after discovering a traumatic brain injury, serious burns to his hands, and bruising.

“James didn’t deserve this. How dare somebody put their hands on him,” said Nicholson. “Jessica how dare you do that to my grandson. You put him in danger, that’s my baby’s baby.”

Rockingham County Attorney Jim Reams said Wednesday the boy is in stable, but serious condition.

“No matter where you go, we’re going to find you. So surrender yourself and let’s do this the easy way,” said Reams.

Arrest warrants are issued and the couple is charged with assault. The search for them has extended into Massachusetts.

On Wednesday night, police received a tip that the pair was spotted at Honey Dew in Lynn.

Police have also been to several places in Haverhill, where they believe Dow has family.

The toddler’s condition is improving.