Elizabeth, the main character, is ambivalent about putting Six-Thirty, a creature with human-like qualities, on a leash.
A leash law is introduced in the city, prompting Elizabeth to reconsider her stance.
She buys a leash and waits for Calvin, another character, to notice. After he doesn't, Elizabeth brings up the topic.
Calvin is dismissive of the leash law, believing it doesn't apply to Six-Thirty, who is well-behaved.
Elizabeth argues that the law is meant for everyone, citing an increase in pet deaths, and mentions that Six-Thirty did not object to the leash on a previous walk.
Calvin likes running with Six-Thirty without a leash and expresses his confidence in their routine.
They discuss the rowing practices and potential participation in a spring regatta.
Despite mutually lying about their enthusiasm, Calvin and Elizabeth contemplate the challenges of the regatta.
Elizabeth heads to work early, leaving a note and breakfast for Calvin.
Calvin reflects on Elizabeth's care for him and his own secret worries about her safety.
Calvin receives troubling letters, one claiming to be from his mother and others demanding money or accusing him of theft.
He laments the loss of a pen pal who stopped writing after Calvin expressed dark feelings about his father.
Calvin decides to keep certain things, like his father grudge, secret from Elizabeth to avoid conflict.
As Calvin prepares for a run to work, he considers how much he's changed for Elizabeth and how much he appreciates his current life.
Before running to work with Six-Thirty, Calvin decides to use the leash due to the darkness and rain.
Calvin clips the leash to Six-Thirty and locks the door, but he is dead within the next thirty-seven minutes.