The Doctor and Peri have been on holiday, visiting old friend Reverend Foxwell in the sleepy English village of Hollowdean. But why are their memories so hazy? Piecing together events they recall a mysterious chauffeur, who is not what he seems, and Foxwell's experiments that could alter the nature of reality. Huge sand creatures have been sighted on the dunes, and many of the locals are devoted to a leader known as 'Professor Stream'. But who is Stream? And what lies within the Hollows of Time? The Doctor will discover that not every question has a definitive answer...