For the second straight day, I felt compelled to ride my bike through the city, pedaling along the Charles River from my home in Cambridge to the foot of Beacon Hill, then through the Back Bay and Kenmore Square. Boston is a beautiful town, especially in the spring. This is the season in which I arrived, in 1997, one of the thousands of young people who flood in every year for school or to start a career. I've left it twice to live in other cities, only to return. It's home.

I felt terrified on Monday, which is what the person, or people, who set bombs at the Boston Marathon finish line wanted. My body shook for hours, as I tried to make sense of the news, of how a gorgeous day out with family had turned into a nightmare. That was what it felt like — when I made it home alone, separated from my husband by the crowd — that I had been lost in a dark dream.

On Tuesday, I rode down familiar, still streets. There was no traffic, no noise. Police guarded barriers blocking off Boylston and sidestreets from the top of Copley Square to Massachusetts Avenue. Workers in the few Newbury shops and restaurants open looked out their doors forlorn. Clergy stood on the corners, ready to counsel anyone overwhelmed. Marathoners in their blue and gold jackets stopped to take pictures and to give reporters interviews. The mood was somber, and people were gentle with each other, every conversation opening with low voices and sympathy. Even the police, directing gawkers from the scene, spoke quietly and with words like Sir, Dear, Miss, please.

On Wednesday, Boston felt like a city alive again. Boylston was still barricaded and investigators in hazmat suits were tossing bags of possible evidence from the roof of a building near Hereford, but children played on the Common and swan boats glided around the Public Garden pond. A hurdy-gurdy busker and his dachshund entertained tourists. A couple paused to kiss on Berkeley. A deliveryman shouted profanities at another driver. Life was going on.

Since Monday, I've been thinking about Patriots' Day and what it means — what it will mean. The only-in-Massachusetts holiday commemorates the battles of Lexington and Concord, the beginning of the Revolutionary War. It is the day of the Boston Marathon, a test of will and stamina for every runner who starts. It will be the sad anniversary of a city devastated. It is about courage.