A Michigan couple faces more than three months in jail and hundreds of dollars in penalties for two overdue library books.

Catherine and Melvin Duren were arraigned Thursday in Lenawee County Court on a misdemeanor charge of failure to return rental property. If convicted, they could be sentenced to 93 days in jail and fined $500 for a Dr. Seuss title that's missing and for a novel that they returned late.

The county prosecutor said the case is necessary to protect taxpayers' money. The Durens said they're being unfairly harassed over a small mistake.

“We were appalled, totally appalled,” said Catherine Duren, 44, according to ABC News. “We didn’t commit a crime.”

The ordeal was set in motion when the Durens' teenage son used his mother's library card in 2014 to check out a Dr. Seuss book from Tecumseh District Library for the couple's granddaughter. That children's book hasn't been returned to the library and is missing.

The charges against the Durens also involve The Rome Prophecy, a thriller checked out in 2015 that was temporarily lost, but was brought back to the library in January, according to TV station WXYZ.

The Durans said they received a bewildering and escalating array of official letters and calls about the borrowed books, demanding late fees and fines and threatening jail time.

The library is charging the couple $55 in late fees and the cost of replacing the lost book. Catherine Duran said authorities refused to accept her money order in that amount because she and her husband balked at paying $210 to the prosecutor's office for a "diversion fee."

That fee funds the prosecutor's economic crimes unit, which investigated the case of the overdue books.

The Durens also paid a $100 bond last week, when they were served with arrest warrants.

Catherine Duran said the couple lives on Social Security, and much of their money pays for medication.

Prosecutions for overdue books have helped the library system defray $10,000 it has lost on unreturned books in a year, according to the Daily Telegram.

“We’re trying to help recover taxpayer money that is flat-out taken from the library," Lenawee County Prosecutor Burke Castleberry told the newspaper.