On a summer's day in Oxford, an old lady who once helped decipher the Enigma code is killed. A strange note indicates that the murder is the first in a series, and each new death is accompanied by a different mathematical shape. A logician and a student team up to find the next clue because the killer can be stopped only if someone can crack the code.

"1895. A senior executive at the Ashmolean Museum in Oxford is found in his office with a bullet hole between his eyes, a pistol discarded close by. The death has officially been ruled as suicide by local police, but with an apparent lack of motive for such action, the museum's administrator, Gladstone Marriott, suspects foul play. With his cast-iron reputation for shrewdness, formed during his time investigating the case of Jack the Ripper alongside...