What is the plot in "The Plot Against People"?

The plot consists of inanimate objects resisting humans with the ultimate goal of defeating us. Life's hard enough as it is, but as part of their dastardly plot, inanimate objects make it just that little bit harder. This is a war of attrition, and inanimate objects are in it for the long haul. So long as they're around, they'll resist us.
In his mock-serious tone, Baker sets out the numerous ways that inanimate objects go out of their way to make life harder for us. Objects have the nasty habit of breaking down just when we need them most. A car, for example, will never break down when it enters a filling station with a large staff of idle mechanics; it chooses instead to wait until it has transported its hapless human cargo to the downtown intersection, right in the middle of rush-hour traffic.
Other inanimate objects are more cunning. They've evolved a much more subtle strategy to make life harder for us: they mysteriously vanish just when we need them. For example, pliers will often manage to climb all the way up from the cellar to the attic, just so they can raise our blood-pressure and make us mad. Keys are more persistent offenders; they have been known to burrow their way beneath three feet of mattresses.