The novel looks at three different stages of his life, his early years in 1922, his time in China, and in particular Nanking in 1937 and back in Tokyo in 1941 in the final days leading up to the Pearl Harbour attack. Niles' character is part Rick Blaine and part Saint Jack, with self-interest and a quick buck seemingly uppermost in every decision he makes. The Casablanca comparison goes further with Niles trying to secure the paperwork that will give him safe passage to Hong Kong on one of the last flights out of Tokyo. As you read, you are never quite sure where Harry's real loyalty lies, which makes the ending all the more satisfactory.
As well as crafting an enjoyable novel, Smith has done a fantastic job of evoking the atmosphere of pre-war Tokyo which must have been the product of a great deal of research. Worth reading.