Police arrested Nicole Vaisey, 25, and Stephen Howells II, 39, and charged them with second-degree kidnapping.
Vaisey allegedly told investigators she and Howells had been planning the abduction for weeks, saying the two were on a "shopping trip" for "slaves."
The pair allegedly drove up to the vegetable stand and waited for the girls to approach the vehicle, St. Lawrence County Detective Sgt. Brooks Bigwarfe told CNN.
Howells then allegedly asked the girls if they wanted to pet the puppy, a Doberman pinscher-golden retriever mix.
The older girl grew suspicious, but Bigwarfe said Howells pushed them into the back of the car.
"When he started forcing them into the vehicle, they were both screaming and yelling," Bigwarfe said.
Vaisey appeared in court Friday, at which time her lawyer, Bradford Riendeau said his client had nothing to do with planning the abduction, she just did as Howells told her to do. Riendeau said Howells and Vaisey were in a master-slave relationship.
"I don't think she had any control over what went on in the relationship. That was the essential ground rule of it," Riendeau said. "He told her what to do."
Howells and Vaisey each face up to 25 years in prison should they be convicted of the kidnappings.