The day the First World War broke out, Alfie Summerfield''s father promised he wouldn''t go away to fight - but he broke that promise the following day.

Four years later, Alfie doesn''t know where his father might be, other than that he''s away on a special, secret mission.

Then, while shining shoes at King''s Cross Station, Alfie unexpectedly sees his father''s name - on a sheaf of papers belonging to a military doctor. Bewildered and confused, Alfie realises his father is in a hospital close by - a hospital treating soldiers with an unusual condition.

Alfie is determined to rescue his father from this strange, unnerving place . . .