Most good stories start with a fundamental list of ingredients: the initial situation, conflict, complication, climax, suspense, denouement, and conclusion. Great writers sometimes shake up the recipe and add some spice.
Initial Situation
Stevens goes on a road trip to the West Country. This is pretty much Stevens's first vacation, and he only lets himself go with the thinly veiled excuse that it is for professional reasons: to see if Miss Kenton will return to Darlington Hall. This road trip gives him a fresh perspective on his life, past and present.
Conflict
When he's questioned by a stranger, Stevens denies ever having known Lord Darlington. His memory goes back to a conference Lord Darlington hosted in 1923. From the beginning, Stevens's association with Lord Darlington is a tad problematic, given Lord Darlington's notoriety as a German/Nazi collaborator.
Stevens repeatedly denies that he knew Darlington, but when he's reflecting on the events of 1923, he defends Darlington—at least, to himself. The year 1923 was also when Miss Kenton and Stevens's father came to work at Darlington Hall, sparking a couple of points of tension in his life.
Complication
Stevens gets stranded in Moscombe and his memories turn toward the 1930s. In Moscombe, Stevens has a feisty political conversation with some locals. He thinks back to when Lord Darlington became more and more involved with the German cause and flirted with anti-Semitism and fascism. It's also a period when Miss Kenton starts dating a former co-worker: ouch.
Climax
At the end of his road trip, Stevens finally meets up with Miss Kenton in Little Compton. His memories turn to the night she announced her engagement, the same night Lord Darlington hosted the German ambassador. Stevens tries to figure out why Miss Kenton left and what he might have done to spur on her engagement.
Suspense
During his conversation with Miss Kenton, Stevens tries to find out about her relationship with her husband. We wait to see if Stevens will ever get around to expressing his feelings or to asking Miss Kenton to return to Darlington Hall.
Denouement
Miss Kenton tells Stevens to let go of the past, which: oof. That has to smart. Stevens never announces his intentions to Miss Kenton, who explains that she loves her husband. Instead, they leave each other as good friends.
Conclusion
On the way back to Darlington Hall, Stevens sits on a pier in Weymouth and tries to come to terms with his past.