The morning after he had been brought by his father to live as a lodger in the back sitting-room of house No. 7, Marco Loristan watched the passers-by on Philibert Place. He was thinking of the long, hurried journey he and his father had made during the last few days—the journey from Russia.

Marco and his father are exiles from the war-torn country of Samavia and members of the secret society devoted to restoring the Samavian throne to the descendant of Ivor, the Lost Prince. When Marco meets The Rat, a crippled London street-urchin, he little dreams of the gigantic and dangerous part he and The Rat will play in the political future of Samavia. 

From the dust jacket of the 1967 J.B. Lippincott reprint edition