The Bassumtyte Treasure by Jane Louise Curry, 1978.

When young Tommy Bassumtyte’s parents died, he went to live with his grandfather. However, his grandfather is now dead, and he is living with his 92-year-old great-aunt, who is in a wheelchair, and her 72-year-old daughter, who has recently had her driver’s license revoked due to her poor eyesight. Although the pair of them have taken good care of Tommy, neighbors have become concerned that they will not be able to do so for much longer because of their age and failing health. Rather than see Tommy sent to a foster home, they decide that he must go to the man who Tommy learns should really be his legal guardian, a distant cousin also named Thomas who lives in the family’s ancestral home, Boxleton House, in England.

The elder Thomas Bassumtyte, who should have taken Tommy when his grandfather passed away, has also since died, but his son, also named Thomas, agrees to take him. Tommy is quickly shipped off to England before there can be a custody hearing in the United States about him because the relatives fear that some official might try to prevent Tommy from being sent out of the country. Tommy is eager to go because he remembers fantastic stories that his grandfather told him about Boxleton House. The current Thomas Bassumtyte also lives there, although the place has become rather run-down, and he fears that he will not be able to keep the place much longer. Thomas was a mountain climber, but he was injured in a fall and hasn’t been able to work much since. He tells Tommy that the two of them might have to move when he is fully recovered and can do more work for the Foreign Office, but Tommy loves Boxleton House from the first moment he sees it and wants to stay.

According to the lore of Boxleton House, a distant ancestor of theirs hid a treasure there, but no one has been able to find it. If young Tommy and Thomas can find it, it would solve many of their problems, and they would be able to keep the house and restore it. All young Tommy has is the mysterious rhyme that his grandfather told him and the strange medallion that his great-grandfather brought with him when he went to the United States in the late 1800s. Thomas tells him that the treasure was supposedly hidden by a distant ancestor of theirs who was fond of riddles, called Old Thomas.

The Bassumtytes were secretly Catholic during the reign of Elizabeth I. Old Thomas was alive then and had a son called Tall Thomas. Tall Thomas traveled frequently and was mysterious about the places he went. One night, he returned to Boxleton House with a young baby, who he said was his son. He had married in secret, and his young wife had died shortly after giving birth. Tall Thomas also brought her body back to Boxleton for burial. However, that wasn’t Tall Thomas’s only secret. Although he remarried, giving his son a stepmother, and lived on for a number of years, he was eventually executed for smuggling messages for the captive Catholic queen, Mary, Queen of Scots. The family was stripped of its noble title and only barely managed to hang onto their house and land. If there was a treasure hidden during this time, it was probably something that the Bassumtytes were afraid would be confiscated by the queen’s soldiers as punishment for the family’s disloyalty or something that Mary had given to Tall Thomas to hide for her.

As Thomas tells Tommy more about the house and the family’s history, he points out Tommy’s uncanny resemblance to Small Thomas, Tall Thomas’s son, as shown in an old painting. Tommy feels a strange connection to Small Thomas, and begins seeing and hearing strange things. An older woman comforts him in the middle of the night, having him recite the same rhyme that his grandfather taught him. A small painting later reveals that this woman was Small Thomas’s grandmother. She appears to Tommy other times, giving him a glimpse back in time and clues to solve the puzzles of Boxleton House.

It is only when Thomas accepts the advice of a family friend who works for a museum that they come to understand the full significance of their family’s heirlooms and the hidden treasure. The treasure may not be quite what the Bassumtytes have always believed it was, but then, the Bassumtytes themselves aren’t quite who they always thought they were, either.

The book is available to borrow and read for free online through Internet Archive.