The danger in writing a novel that’s largely devoted to the mundanities of domestic life is that the novel itself can take on the dreariness of the chores and homework, the grocery shopping and stubborn stains that fill its pages. Good To A Fault, the second novel by Canadian theater-director-turned-novelist Marina Endicott, is an understated examination of when “being good” shades into ugly self-interest, and Endicott has a keen ear for the often-conflicting emotions at play behind our must humane impulses. But the book’s dramatic peaks and troughs can run so slight as to be nearly undetectable, and when heated conflict does arrive, it almost feels like an intrusion from another story.

In the book’s first and most tumultuous scene, Clara Purdy’s respectable workaday existence intersects with the itinerant Gage family during a car accident—a crash with a minimum of bloodshed, but violent consequences. When the mother, Lorraine Gage, is diagnosed with lymphoma and separated from her family by chemotherapy and pain medication, Clara steps into the maternal role, quickly discovering more satisfaction in caring for her surrogate children than she ever did holding down her job as a claims adjustor, or maintaining the museum that is her parents’ old home.

Good To A Fault’s perspective jumps fitfully between the members of the ad hoc family, and some of its best moments are spent following Lorraine’s precocious daughter, Dolly, as she snoops into strangers’ homes and escapes into Jane Eyre and Mistress Masham’s Repose. They’re stories about orphans, but fiction lets her keep her mother’s illness at arms’ length. An Anglican priest who takes an interest in the family has a similar coping mechanism: When his own words fail him, he always has a snatch of poetry ready to substitute. Together, they present a moving portrait of the ways art can function as salve and shield.

Ultimately, though, this is a book about Clara’s guilt and how she processes (and reprocesses) it. It’s engaging at times, and Endicott brings some real insight to the ways in which people cling to and then discard each other as their needs change. But the book’s middle sags underneath layers of sentiment, as paragraph after paragraph ends in tears either bitter or rapturous.