Mark and Carol own a four bedroom house on Long Island. They are raising three children, all under the age of 10. Mark is a private investigator. And Carol is a stay-at-home mom.

One day, two solicitors from the Jehovah's Witnesses make a house call. Carol invites them in. Six months later, she secretly joins the organization. When her conversion finally goes public, their marriage, home, family and social life are almost destroyed. Carol abandons all her friends and begins devoting her time and energy to serving this new cause.

The children, caught between two faiths, are confused and put in harms way. Their relatives and friends suffer. The marriage almost crumbles. In the end, Carol knocks on the wrong doors with her partner and pays the price.

The family struggles to stay afloat in this storm.

John J. Hart worked as a private investigator in New York for close to 20 years, providing a good background for digging into a subject with objectivity and producing clear information. After moving with his family to West Virginia, he started Wild Wood of West Virginia, producing original wooden toys on rockers, which appeared in the Smithsonian, Colonial Williamsburg, and QVC.

In retirement, he enjoyed writing romantic novels with a serious twist, exploring cults, their history, and how they line up with Christianity. A Knock at the Door is a response to a close friend's family being all but destroyed by the Jehovah's Witnesses.