The following version of the book was used to create this study guide: Heiny, Katherine. Early Morning Riser. Penguin Random House, New York, NY, 2021. Kindle AZW file.

Jane Wilkes arrives in Boyne City, Michigan, buys a house, and settles into a job teaching second grade in the local school. She meets Duncan Ryfield when she locks herself out of her house. He finds a way in through a bathroom window, and she impulsively invites him to dinner. That evening turns into a relationship, and they are soon dating. Jane's only other friend in town, a high school music teacher named Frieda, warns that Duncan has slept with almost every woman in town. Duncan does not deny it. He even admits to having slept with his ex-wife, Aggie Polnichik a few years ago, despite the fact they have been divorced for years and Aggie is married to an insurance agent named Gary. Jane expects her relationship with Duncan will lead to marriage. When he makes it clear it will not, they stop seeing each other.

By this time, Jane has become friends with some of Duncan's friends, including Aggie and a man named Jimmy Jellico. Jimmy has developmental issues. Duncan employs him because he knows Jimmy could not find another job. When Jane plans her wedding to Luke Armstrong, Duncan's current girlfriend is the photographer. Jimmy is the usher. The evening after the rehearsal dinner, Jimmy's mother remembers that her purse is at Jane's house. Jane, desperate for time alone after the entire day with her mother (Phyllis) and Luke's mother, instructs Phyllis to take Mrs. Jellico home. Phyllis has an accident on the way, and Mrs. Jellico dies. Jane, who feels guilty that her mother was to blame for Mrs. Jellico's death, takes over Jimmy's finances and oversees many of his daily activities. She finally admits she does not want to marry Luke at all, and she begins seeing Duncan again. Jane is surprised when Jimmy has a new friend, an older man named Willard Williams. Jane is horrified a few weeks later when she learns Willard convinced Jimmy to take out a large mortgage on his house and then stole the money. Duncan and Jane know Jimmy will lose his house. Duncan proposes, saying the only way to deal with the situation is to get married, buy a larger house, and provide a home for Jimmy. Aggie helps sell Jimmy's house to pay off the mortgage. Additionally, she sells Jane's small house and finds a house for Jane, Duncan, and Jimmy to call home. Duncan soon suggests they have a baby. Within a few years, their family is complete with two daughters.

Through the years, Jane continues to teach and feels she has missed out on things in her life. She is married to Duncan but worries that he still loves Aggie. She feels she does not measure up to Aggie and that she should. Also, she feels saddled with the responsibility for Jimmy. In a series of epiphanies, Jane realizes she has a wonderful life. She understands that Duncan truly loves her and is just friends with Aggie. Also, Jimmy is a full member of her family.