David Cunningham

The Alden children, isolated in a storm at a small bus station, are led into a mystery centering on a polluted river.

Two brothers take summer jobs at a department store where a series of peculiar events brings them under suspicion.

A friendly writer with a metal detector, the mysterious inhabitants of a tower house, and the discovery of a locket in the sand are ingredients for the Aldens' latest mystery.

When the Aldens spend the summer riding on a train, they get to live in a train car once again - this time, they're staying in Caboose No. 777. The number is hard to forget, and indeed, the children meet people at each stop who seem to know it well. It turns out Caboose No. 777 has an unusual past - one that comes with its very own mystery!

The Alden family rents a houseboat to drift down the river, and encounters a mystery in the little towns along the river, involving a fast black car.