Cate herself is certain of nothing. Life seems at once becalmed and full of danger, as though a wave could come at any moment, rising out of the still waters, a great towering wave, and take her down.

She receives her finals results. She has scraped a first-class degree. She tells Hannah, who looks shocked. “It was an accident,” says Cate hurriedly. And then hates herself for saying it. Still, she thinks, it was an accident. She never expected that.

Her tutor calls to congratulate her. “So what are you going to do?” he says.

She can only think that she would like to tell her mum. To give her the good news.

SHE GETS AN email from Hesther, a friend from Oxford who is living in Brighton, inviting her down for the day. There is a room available in her house.

As she steps off the London train, Cate can smell the sea. She walks down to the seafront and stands on the pebbled beach and stares out at the pale horizon. She walks through the city to Hesther’s house. Brighton seems appealingly ramshackle, human-sized. The room is cheap and small with a window that lets in good light. She takes it. She buys herself some furniture from the charity shops on Lewes Road.

The other room is occupied by a woman called Lucy. Lucy wears combat pants and vests and boots with thick soles, as though she is a foot soldier in an unnamed war. She has thick dreadlocks that hang down her back, and her face is small and fine. She is studying for a master’s in international development at the University of Sussex. She is half American—grew up between Devon and Massachusetts, and her accent is deliciously confused. Two summers ago Lucy lived up a tree in Newbury, sleeping on a wooden platform a hundred feet above the earth, protesting the destruction of ancient woodland for the building of a highway.

Lucy teaches Cate how to use a drill, how to put up shelves in her room. She has a light cloud of armpit hair and does not use deodorant. When they stand close, Cate catches her musky scent. Walking around the city with Lucy is an education—she has a scavenger’s eye: wood for the wood burner, wine crates for shelves, just-out-of-date food from supermarket clearance bins. Lucy carries herself lightly, as though she still walks in the forest. As though at any moment she might be predator or prey.