SACRAMENTO, Calif.—Prosecutors say a Northern California couple accused of imprisoning their 13-year-old son for days by locking him in chains, often tethered to a kitchen table, has been charged with felony child endangerment.

Forty-one-year-old John Vang, the teen’s father, and 34-year-old Thong Vue, the boy’s stepmother, appeared for arraignment Monday in Sacramento Superior Court, but they didn’t enter a plea. They will return to court Aug. 18.

The couple is free on bail. They wouldn’t talk to reporters.

Investigators say the boy was wrapped in chains—with padlocks securing each ankle and a long chain connected to the padlocks—for days until he managed to escape July 30 and flag down passers-by for help.

The teen is now in the custody of his biological mother.