'Creepy-Mouse Coming to Get You' by Barbara Holland (1985)
Houghton Mifflin, 1985
From the jacket copy:
"With their mother away at work, it is up to Jeremy to think of a way to protect his sister and her baby from the dashing yet violent man she shouldn't have married.
"A fort in a vacant lot, a pet garter snake named Glatisant, and a surprising weakness ... all play a part in the dramatic conclusion to this offbeat story of suspense."
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