ST. LOUIS — Adam Smith said he and his 45-year-old sister have wondered all of their lives what their mother was keeping inside a cardboard box in her freezer. Early Sunday, the nearly four-decade-old mystery took a turn that he describes as “crazy.”

Smith began clearing out his mother’s belongings from the Clifton Heights apartment, where she had lived for more than 20 years, after she died from lung cancer July 21. She was 68. When he got to the box early Sunday, he took a picture of it and told his girlfriend that he was about to open it.

He said he thought he would find the top of his mother’s first wedding cake. Or maybe some money, because she never had a bank account. Instead, he said he found a pink blanket and the mummified remains of a newborn.

He called police. St. Louis homicide detectives are handling it as a “suspicious death.”

Meanwhile, Adam Smith said he can’t stop trying to figure out who the baby is, and how it got there. He said he’s hoping an autopsy may bring him some answers, and he gave police a DNA sample after being questioned for two hours.