Trenton police charged 33-year-old Plesie Nichols and her 28-year-old live-in boyfriend Anthony Roberson with aggravated assault and child endangerment.
Police say it was on May 19th when officers went to the home at 146 S. Logan Avenue and found the girl with serious injuries to her arms.
Those injuries, police say, were from being tied up by Nichols and Roberson.
"The injury was so severe it was possible the child was going to lose her arm," said Acting Mercer County Sheriff Jack Kemler.
Officers were there on an unrelated custody matter when, they say, the little girl begged them to rescue her.
"She spoke to me and said to me 'Can you please take me away from her?'" said Ofc. Bruce Armitage of the Mercer County Sheriff's Department. "I asked her why she wanted to be removed from the home. She said 'Because my mother beats on me and she doesn't feed me."
The girl weighed just 40 pounds, police said.
The couple was also charged with possession of a weapon for unlawful purposes. That was the rope and shoelaces that prosecutors say was used to tie the girl to a banister and doorknobs.
Police say the conditions in the house were among the worst they'd ever seen.
"The floors were covered with rotten garbage, rotting food, dead rodents, some live rodents," said Ofc. John Mendez.
The girl was also severely malnourished, according to police.
The girl was rushed to Mercer Hospital Pediatrics Express and then transferred to St. Christophers Hospital for Children in Philadelphia to be treated for her wounds.
Three other children - age 7 months, 1 and 4 years old - were also rescued from the house.
The mother and boyfriend are each held on $150,000 bail. It's not clear whether they've retained lawyers.