The 11-year-old boy was discovered, shivering and alone, restrained by a handcuff around his ankle, the Monroe deputy sheriff said in a statement.
Sheriff Eddie Cathey called the incident "shocking" and pledged to pursue the investigation "to its fullest extent."
The officer was responding to a complaint next door when he noticed the child and initiated an investigation, ultimately removing five children from the home.
"While not present at the time the children were discovered, Larson is accused of being complicit in the ongoing mistreatment of the children," authorities said.
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The couple had adopted four of the children, aged 8, 9, 13 and 14, and were serving as foster parents for the 11-year-old found on the porch.
They have both been charged with "intentional child abuse -- inflicting serious injury, false imprisonment, and cruelty to animals (based on the condition of some of the family pets as well)," the statement said.
She is being held on USD 525,000 bail, while Lee's bail has been set at USD 500,000. They are due in court tomorrow.