The Smithsonian Institution - Gore Vidal

Good Friday, 1939, and T., a sixteen-year-old schoolboy, arrives at the Smithsonian Institute in Washington. The museum is closed, but T. manages to slip in, and it would appear that somehow, he is expected. An old man, Bentsen, shows him around, and T. realises that all is not as it seems. As he goes to examine a Native American exhibit, he is drawn magically into the nineteenth-century world of a reservation of Sioux Indians. They like what they see of T. and immediately get the pot boiling. T. is forced to take refuge in the tent of a young Squaw. They become lovers, and she helps him to escape back to the safety of the Smithsonian.

Back with Bentsen, T. explores the Smithsonian further and begins to fathom the mysteries of time travel. The Smithsonian scientists have discovered how to get back to the past, but still don't know how to travel to the future. T. puts his brilliant mathematical brain to the problem. However, given a glimpse into the future, T. sees his own untimely death, and becomes determined to prevent the outbreak of WWII...