The Mystery of the Emeralds — Kathryn Kenny

It was a small plot, enclosed by an ornate iron fence. The gate was ajar, and, going through it, Trixie and Jim saw rows of moss-covered headstones. In the rear was a small but impressive marble mausoleum.

"Ooooh! Cemeteries give me the shivers!" Trixie exclaimed.

A sudden clap of thunder made them both jump, and they hurried to the vault. By now the rain was teeming, and the inside of the mausoleum was pitch black, but at least they were out of the storm...