he Brown Fox Mystery (1948)

When those two enthusiastic fishermen, Djuna and his friend Tommy, are offered a chance to spend the summer at fish-filled Silver Lake, as the guests of Miss Annie Ellery, they are overjoyed.
But great as the fishing proves to be, there is more in store: Silver Lake holds a mystery and the boys find themselves swept up in a series of exciting and dangerous adventures, involving an abandoned ice-house and two fires, as they help to solve it.

When Djuna and his best friend, Tommy Williams, set off with Miss Annie Ellery for a holiday on Silver Lake, the thing they look forward to most is fishing.
They acquire brand new fishing rods and tackle, and when they arrive at the lake there is Cap'n Ben, owner of a fine old motor boat, all ready and delighted to show them just where the big ones are.
Almost anybody ought to be satisfied with such a set-up for a pleasant and exciting summer, and there's no question that Djuna and Tommy are. But the real story in this book is what happens after the fishing and the boating begin. A heliograph belonging to Don and Andy McKelvey has something to do with it, and so does an abandoned icehouse, two fires, a couple of mysterious characters and a harrowing search for a missing person.

Everyone who has ready any of the previous stories about Djuna and Miss Annie by Ellery Queen, Jr. , knows there will be first-class entertainment in this one. Anyone who likes a thrilling story about boys who really use their wits when they are enjoying themselves, as well as when they get into jams, will find this one made to order.