The alleged kidnapper, Neelam, was caught near Pari Chowk here.
The Shahjahanpur native had befriended the infant's mother. Yesterday afternoon she took the boy with her to a market, but did not return.
The child's mother informed police after being unable to locate them.
On interrogation, Neelam told police she was planning to sell off the boy to a trafficking gang.
She was produced before a magistrate and sent to judicial custody.