“What no wife of a writer can ever understand is that he’s working when he’s staring out the window.”

That classic observation from the late author and journalist Burton Rascoe ranks among my favorites, although my wife is quite a window-watcher herself and doesn’t really begrudge me my own daydreaming.

Rascoe’s point is that we’re often at our most creative when our mind is lying fallow, emptying itself of clutter so that it can be refilled with something better. This basic principle of rest applies to other forms of work besides writing, of course, and it’s a particularly useful idea to keep in mind during the summer, a season supposedly given over to slowing down and recharging one’s batteries.

All of this came to mind the other day when I learned about what the late mystery writer Agatha Christie saw when she looked out her summer library window. Beyond the panes of Greenway, Christie’s secluded estate in Devon, England, was the River Dart, a meandering waterway that probably transported Christie on quite a few daydreams when she glanced from her reading chair during the vacation season. Greenway is now open to tourists as a historic house.

I’ve been learning about Greenway through a lively article about the Christie estate in the June issue of Smithsonian. The story is also at http://www.smithsonianmag.com/travel/Where-Agatha-Christie-Dreamed-Up-Murder.html.

This is a time of year when a lot of media busybodies, including me, tend to tell readers what summer books to read, but I could probably pass from May through August each year by doing nothing but catching up on magazines I haven’t read. Our 10-year-old son, who’s getting through the summer on back issues of Popular Mechanics, is already learning this lesson for himself.

Christie has also been on my mind lately because public television’s “Masterpiece Mystery!” series has four new Christie whodunits starting this Sunday night at 8, with new episodes each Sunday through July 10. In the first three mysteries, David Suchet reprises his role as Hercule Poirot, the portly Belgian detective who works in Depression-era England. The fourth mystery in the new batch is a “Miss Marple” production with Julia McKenzie in the title role as the enterprising spinster sleuth.

The landscapes of these TV productions are as much a character as the cast members, especially in the “Poirot” shows, where the lavish art deco detail instantly transports the viewer to an England beginning to darken under Hitler’s shadow.

When soldiers billeted at Greenway during World War II, they painted a vivid battle scene in Christie’s library. Christie kept the mural intact after the war, and it became a part of her household. Christie had a gift for domesticating violence as an object of art, which anyone who samples her murder mysteries quickly finds out.