The Middle Ages were not only a time of endless wars and epidemics, but also an era of scientific discoveries and a selfless pursuit of knowledge. Medieval thinkers and practitioners explored the world around them, founded the first universities, invented mechanical watches and instruments for observing celestial bodies. In this book, our guide to the world of medieval science will be a real person, a monk named John Westwick, who lived in the 14th century and was educated in largest monastery in England. The fascinating history of his scientific works allowed the author to show not the ceremonial world of star names and discoveries, but the atmosphere of scientific research of that time, to present the ideas and achievements of the nameless majority of people with a scientific mindset, which so often elude the attention of historians. Traveling with brother John across Britain and beyond, we will meet curious characters of those years: an English watchmaker abbot, a French artisan turned spy, a Persian polymath who founded the most advanced observatory in the world. We will find out how these people navigated by the stars, multiplied Roman numerals, treated illnesses and determined time using the astrolabe, and we will reconsider the attitude towards the Middle Ages as dark times.