Treasure chest (Ann Hood)

When their parents divorce, twelve-year-old twins Felix and Maisie move with their mother to live in the attic of a historic Newport, Rhode Island, mansion where they discover a hidden room that carries with it an intriguing secret.

"When Felix gets a crush on his friend Lily, who was adopted from China as a baby, he decides to try to take her back in time to learn more about China. After being caught by Maisie, the twins find themselves transported to a small village on the Yangtze River, leaving Lily behind in the present. In China, the twins meet Pearl Buck in the days just before the Boxer Rebellion. With bandits chasing them, they flee to safety in Shanghai. The twins return...

"Felix and Maisie re-enter The Treasure Chest and suddenly find themselves in the midst of a Lakota village. While exploring they meet a young man, soon to be known as Crazy Horse--and embark on an adventure that includes fascinating vision quests and exciting battles"--

"Time travelers Maisie and Felix meet a young Alexander Graham Bell (the inventor of the telephone). When the twins get separated from Alexander, they join the thousands of orphans in the streets of Victorian London"--