The story of the adventures in space and time of Meg, Charles Wallace, and Calvin O'Keefe (athlete, student, and one of the most popular boys in high school). They are in search of Meg's father, a scientist who disappeared while engaged in secret work for the government on the tesseract problem.

Eight-year-old cousins Patrick and Beth find themselves 1450's England during the War of the Roses, where they discover the missing treasures and meet the person who has been sending notes through the Imagination Station.

When the Imagination Station sends time-traveling cousins Patrick and Beth to a ship that is captured by the British during the Revolutionary War, they are befriended by James Forten, a free Black of Philadelphia, and help save the life of an imprisoned boy dying of scurvy. Includes a secret word puzzle.

"Jack and Annie are about to meet the fiercest warriors of all--the soldiers of the ancient Roman legion! When the magic tree house whisks them back to a ROman army camp, they learn their mission: Be like warriors. That is easier said than done--Roman soldiers are the best fighters in the world! When Jack and Annie find themselves in the wrong place at the wrong time, they're in big trouble. Who will save Jack and Annie?"--Page [2] of cover.

Beth and her cousin Patrick travel in Mr. Whittaker's invention, the Imagination station, to 1000 A.D. Greenland, where they meet Erik the Red and Leif Eriksson and witness the spread of Christianity in that country.