MINNEAPOLIS — When a brain tumor took away Dorothy Holm’s ability to speak, she picked up index cards and began filling them, edge to edge, with seemingly random, indecipherable sequences of letters. Her grandchildren saw her scribbling and thought she was leaving them a code — but it was one the preteens couldn’t crack.

Eighteen years later, the puzzle has been solved after one of Holm’s granddaughters posted images of a card online. In just 13 minutes, a MetaFilter.com user figured out that as Dorothy Holm was dying, she was writing out prayers.

“It was kind of relieving to have an answer, even if we don’t know what every single word says,” Janna Holm, who posted the card, said. “It’s nice to know that they were prayers, and kind of gave some insight into what she was thinking and what she was focused on in her last couple weeks.”

Holm said Wednesday that her grandmother, who lived in Shakopee, was diagnosed with lung cancer that metastasized and formed a brain tumor. She died in 1996 when Janna was 11. In her final weeks, she wrote line after line of capital letters on roughly 20 index cards, sparking her grandkids’ curiosity.

Holm said she, her brother and two cousins — then ranging in age from 8 to 12 — spent a few months trying to figure out what the letters stood for, but failed.