Not so much "Why?" as "What resulted?" The chicken startles cows who cross a dilapidated bridge, which then collapses onto a train allowing the escape of a burglar, etc. This hilarious sequence moves forward at breakneck speed, but is more than a simple chain of events since characters reappear and some events have further, delayed consequences; moreover, the whole is circular, the last event reiterating the first. Sly asides ("Who ordered their beef rare?" as cow falls on table) add to the delight. Deceptively cartoonish, Macaulay's boldly patterned and colored illustrations are skillfully designed as well as broadly humorous. Add this to the growing collection of picture books with a lot to offer older, slower readers.