Fog, a cloud that touches the ground, marks the fuzzy and shifting boundary of just how much (or little) we are willing to tolerate the natural world. Viewed from beyond the fog line, it is picturesque, the stuff of postcards and viral videos; yet from within it is a menace, responsible for travel delays, accidents—including the deadliest airline disaster in history—and is a vessel of terror and contagion. Stephen Sparks traces the brief history of fog from the mid-19th century, when Oscar Wilde claimed that fog was invented, to the 21st century Pacific coast, where scientists believe fog may be going extinct, to reveal a history of our conflicting desires to eliminate and appreciate fog.