A particularly challenging aspect of the writing craft is to braid a storyline set in the present with one set in the past. Full Dark House starts in the present day when recently retired detective Gladys Forthright is awakened in the middle of the night by a phone call saying that a bomb has destroyed her former station house. She rushes to the scene where she is met by her long-term colleague John May. Knowing that his partner Arthur Bryant planned to work there all night, May fears the worst.
Certain clues indicate that the explosion is related to the very first case that May worked on with Bryant, when May first joined the Peculiar Crimes Unit—peculiar meaning “special” but given Bryant's interest in the paranormal it quickly came to mean something entirely different. That first day Bryant and May began investigating the gruesome murder of a dancer during World War II. The dancer was preparing to perform in a new production of Orpheus at the Palace Theatre, which was meant to raise the morale of Londoners buffeted by wartime shortages and the constant threat of German bombing raids.
The easiest approach to combining past and present is to have the present-day story as a frame: only at the beginning and the end of the book. Brideshead Revisited is an excellent example. Another approach is to introduce each chapter with a bit of the present-day story and then move back into the past, as Jane Urquhart did so well in Away. A third way is to alternate chapters, which Fowler does here effectively.
The main thing is to be sure the reader knows what time period she is in, so having a consistent format, such as the three above, helps by telling the reader what to expect. Recently I heard of a work-in-progress, a novel, set entirely in today except for one flashback scene near the middle. While I believe a talented writer can make anything work, I suspect that scene will leave readers disoriented.
Another way to help readers figure out where they are, as I learned from my friend Pat, is to provide clues in the text that signal one time frame or another. Fowler does that as well. In the present, May complains about his elderly aches and pains, while in the past he's sprightly enough at nineteen to jump on a motorcycle and endure a grueling pursuit. Also, Bryant's presence is a clear marker that we are in the past. The time periods, too, are quite different: the present prompts May's complaints about traffic and ugly architecture, while the past conjures up the blackouts and sirens of the Blitz. Also, some characters only exist in one timeframe or the other.
In addition to managing the time shifts so that I was never unsure of what time period we were in, Fowler crafts a satisfying puzzle, both in the past and the present. Bryant and May make an interesting team. May knows how to attract the ladies while Bryant hopelessly fumbles every encounter. Bryant's partiality to paranormal explanations is lost on May with his resolute practicality. When the Palace appears to be haunted by a phantom, the two come up with dramatically different explanations. If I anticipated some aspects of the ending, others took me by surprise. This is the first in a series of books about Bryant and May, and it is well done indeed.