Alexander was supposed to bring the child to day care when she picked her up Tuesday morning, ABC News station WABC-TV reported.
More than 15 hours later, Alexander returned the toddler to the child’s home today just after midnight, police said, describing the pair as in "good condition." After a subsequent investigation, the nanny was arrested and charged with kidnapping, endangering the welfare of a child and unlawful imprisonment, police said.
Alexander had worked with the family for more than a decade and had no known medical problems, WABC-TV reported.
The child was taken to the New York Downtown Hospital for evaluation, according to the station.