What would compel [the late actor Alec Guinness,] this most reserved and private of superstars, to run through a London street and then fall on his knees?

In his autobiography, Blessings in Disguise, the actor described one such scene: "I was walking up Kingsway in the middle of an afternoon when an impulse compelled me to start running. With joy in my heart, and in a state of almost sexual excitement, I ran until I reached the little Catholic church there … which I had never entered before; I knelt; caught my breath, and for 10 minutes was lost to the world."

Guinness was at a loss to explain his actions. He finally decided it was a "rather nonsensical gesture of love," an outburst of thanksgiving for the faith of the ages. The actor dashed into that church not long after March 24, 1956, when he converted to Roman Catholicism and ended his pilgrimage from atheism to Christianity.

The actor liked to quote the witty British writer G.K. Chesterton, who said: "The Church is the one thing that saves a man from the degrading servitude of being a child of his time…."

Guinness took his first steps to faith while playing Father Brown, Chesterton's great detective-priest. Shortly before work began on the 1954 film, which in America was called The Detective, the actor's young son, Matthew, was stricken by polio. As Guinness walked home each night from the studio, he began visiting a Catholic sanctuary, to sit—alone.

Finally, he struck what he called a "negative bargain" with God. If his son recovered, Guinness vowed never to prevent the son from converting. Soon the boy walked, and then ran. The next year, Guinness made the first of many retreats to Mount St. Bernard Abbey.