Now happily establshed with their grandfather, the 4 Aldens finish the school year looking forward to a promised surprise. Grandfather owns an island, and they are going to live in a house on it for the summer! But who is the mysterious young man staying with the fisherman, the only other resident on the island?

Violet and Jessie begin an adventure when they journey to Centerville to keep Aunt Jane company on the family ranch.

The adventure begins when the entire town of Yellow Sands is left puzzled by a mysterious fire. Henry, Jessie, Violet and Benny have returned to Mystery Rancy for their summer vacation, and they find themselves reunited with their summertime friend, Mike. Mike has been wrongly accused of starting the fire, but with the help of the Boxcar children, he uncovers the real culprit.

While on a bicycle trip to their aunt's farm, the four Aldens help solve a mystery.

Six children help solve the mystery of a missing spyglass that has kept two brothers feuding for years.

A family starts out on a one-day mountain climbing excursion that becomes very exciting. In fact, it becomes an adventure for the former "boxcar" family. They unearth some mysteries and have a fine time in the process.

A young Canadian visitor helps the Alden family solve a mystery involving a lost coin collection.

Henry, Jessie, Violet, and Benny become trapped in a cabin by an unexpected snowstorm, which turns into an even greater adventure when they help their neighbors, a baker and his family, recover an old family secret.