The general story has been told before, but this is the first close look at Ted Hall, one of the most important of the Soviet spies who passed to his masters many of the secrets of the atom bomb. Hall was a brilliant and immature physicist who subsequently fled to Great Britain. He cooperated, to at least a limited degree, with the authors of this story, who have also drawn heavily on declassified documents, including, in particular, decrypted Soviet communications with their agents in the United States. Eeriest of all is Hall's concluding two-page letter to the authors; unrepentant, the aged traitor contends that the 19-year-old youth "had the right end of the stick."