The Golden Eagle Mystery (spoilerish)

 The Golden Eagle Mystery (1942) by Ellery Queen, Jr.

Djuna and his Scottie dog Champ are all set to spend a quiet summer on the coast with "Aunt Patty" (everyone calls her that). He's looking forward to swimming and sailing and making new friends...and finding out what's bothering Aunt Patty. Miss Annie Ellery (with whom he lived) had sent him to Aunt Patty with instructions: 

Go and find out what the trouble is at Aunt Patty's house. There's trouble of some sort. She may even be in great danger. But, if you ask her, she will probably say there's nothing wrong at all. Just go there and keep your ears open....Listen to what her neighbors say there in Stony Harbor, and find out for yourself what is worrying her. No one need ever guess that a boy like you is a real detective.

So, he follows instructions. He makes friends with a boy named Billy. He meets the neighbors. He begins to suspect that Aunt Patty's worries are money-related. And up in Aunt Patty's attic, he and Aunt Patty finds a bunch of letters from her great-grandfather with clues to a missing treasure. He also finds some slips of paper that refer to a golden eagle as well as a nest egg being "put  where it be." When egg-shaped items begin disappearing from Aunt Patty's house, he's sure that there is something valuable to be found and he enlists Billy's help in tracking it down.

***********Possible Spoiler Ahead!************

As with most of these Ellery Queen, Jr. stories, the mystery is pretty straight-forward and doesn't take much guesswork. To be quite honest, all I needed was the title and I knew what it was all about. But also as is generally the case, the characters are engaging and there is adventure and mystery enough for the young readers who are the target audience for these books. Djuna and Champ are great leads and the friends they make along the way in their adventures are well-drawn. A good solid mystery. ★★★

First line: The new boy closed the door behind him and looked up and down the unfamiliar street.

Last line: "Gee," he said, "Alberto's going to miss Champ a lot!"
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Deaths= one drowned