Part One spans approximately seven hours and takes up more than half the book. It’s set at the Ramsay’s summer home, where the Ramsays and their eight children are entertaining a number of friends and colleagues. The novel begins with James Ramsay, age six, wanting to go to the Lighthouse that’s across the bay from the Ramsays’ summer home. His mother, Mrs. Ramsay, holds out hope that the weather will be good tomorrow so they can go to the Lighthouse, but Mr. Ramsay is adamant that the weather will be awful. Charles Tansley, one of Mr. Ramsay’s visiting students, chimes in and supports Mr. Ramsay’s view that the weather will be rotten. He’s a very socially awkward young man who is obsessed with his dissertation.
Numerous small bits of action occur. For example, after lunch, Mrs. Ramsay takes pity on Mr. Tansley and asks him to accompany her into town. By the end of the trip, Mr. Tansley is in love with the much older, but still beautiful, Mrs. Ramsay (by the way, she is 50). Later, as she sits in a window and reads a fairy tale to James, Mrs. Ramsay remembers that she must keep her head down for Lily Briscoe’s painting. (If you’re wondering who Lily is, we are in the same boat. Although, we gather she’s a family friend.) Mrs. Ramsay has the fleeting thought that Lily will have a hard time getting married, but she likes Lily anyway and decides that Lily should marry William Bankes, an old friend of Mr. Ramsay’s.
William Bankes, who is also visiting the Ramsays, comes up to Lily and the two of them go for a walk. They talk about Mr. Ramsay. Meanwhile, Mr. Ramsay walks along the lawn and worries about mortality and his legacy to humankind, and then pesters Mrs. Ramsay to soothe his ego. Mrs. Ramsay does calm her husband, and then starts worrying about Paul (the Ramsays’ guest), Minta (another guest), Nancy Ramsay (daughter), and Andrew (son), who are not yet back from the beach. She hopes that Paul has proposed to Minta.
At dinner, Mrs. Ramsay triumphs. The food is delicious; she is beautiful; Mr. Bankes has stayed for dinner; and Paul’s proposal to Minta has been accepted. She wishes she could freeze the moment but knows it is already part of the past. She tucks her youngest two children into bed and then sits with her husband as he reads. They make small talk and she knows he wants her to say, "I love you," though she refuses. She gets out of it by smiling at him and telling him that he was right – the weather will be bad tomorrow and they will not be able to visit the Lighthouse.
Part Two compresses ten years into about twenty pages. All the traditionally important information in a story (read: what happened to the characters) is briefly imparted in brackets. We learn that Mrs. Ramsay, Prue Ramsay (daughter), and Andrew Ramsay (son) have died. Mrs. Ramsay died at night; Prue died in childbirth (after first getting married); and Andrew died when a shell exploded in France. Oh, right. There also happens to be a war going on – World War I – which gets glossed over in favor of extended descriptions of the weather and the summer house by the sea.
Part Three takes place at the summer house and begins with Mr. Ramsay and two of his children, Cam and James, finally going to the Lighthouse, and Lily working on the painting of Mrs. Ramsay that she never finished. Via Lily’s thoughts, we hear that she never married, but remained good friends with William Bankes. Paul and Minta’s marriage fell apart. Mr. Ramsay, Cam, and James actually make it to the Lighthouse. Lily finishes her painting. Throughout this last part of the novel, it’s clear that Mrs. Ramsay is sorely missed.