Get out the microscope, because we’re going through this poem line-by-line.
Then he climbed the tower of the Old North Church,
By the wooden stairs, with stealthy tread,
To the belfry-chamber overhead
- Now that he knows what Paul wanted him to find out, our guy in Boston heads up to the top of the North Church to finish his job.
- He climbs up with "stealthy tread," which means he steps quietly and carefully. That highlights how dangerous and secret this mission is, and it's also a nice echo of the "measured tread" of the soldiers in line 29.
And startled the pigeons from their perch
On the sombre rafters, that round him made
Masses and moving shapes of shade
By the trembling ladder, steep and tall,
To the highest window in the wall,
Where he paused to listen and look down
A moment on the roofs of the town,
And the moonlight flowing over all.
- Longfellow takes his time with this description, building up suspense instead of pushing the plot along.
- He tells us all the details about the church tower, right down to the pigeons that live up there. It's another spooky little side-story, complete with creepy shadows, a rickety ladder, and a view of the town in moonlight. As you can see, there's tons of mood in this poem.