Cressida Connolly’s new novel begins with a couple of endings. It’s spring 1855, and on the battlefields of the Crimea William Gale is mourning the deaths of his brother Algernon and his friend Mr Lockwood. He writes to his wife Alice, who back home has befriended the progressive Dr Nolan, and asks her to call on Mrs Lockwood in Cheltenham. Upon returning from the war a medalled hero, William isn’t himself, and after meeting the ‘good lady’ widow and her two little girls, Molly and Kitty, he makes a rash decision that reverberates across generations.

It’s hard not to play favourites with a novel divided into three fairly distinct parts, and I admit I would happily have spent all 280 pages of Bad Relationsin Part Two. The year is 1977 and William’s descendants have invited Stephen Nolan, a thoughtful art school drop-out (and a distant relative) to help on the family farm in Cornwall. Enamoured of the charismatic Clarke girls, Cass and Georgie, and Georgie’s London friend Helena, Stephen spends the summer in an acid- and sex-fuelled haze, which is abruptly brought to a tragic close.

It’s testament to Connolly that each section can be appreciated both on its own and as a part of a well-matched triptych. The panoramic tale is told in the close third person, the voice shifting to suit the times. Throughout are sweet and funny observations: Alice’s feelings are like ‘a bramble spilling over a broken wall, a tangle of leaves and reaching stalks, hidden thorns, bright tiny insects moving among the small white flowers’; Dr Nolan is ‘one of those unfortunates whom nature required to shave twice a day if he were to maintain a semblance of neatness’; and Stephen is dazzled by Cass’s looks – ‘the kind of beauty that you saw on the posters advertising foreign films’ – then relieved to find that she walks with ‘a sort of trudge, head forward, that was reassuringly like a human girl’.

Part Three transports us to 2017 and throws light on the consequences of William’s actions and those of his descendants. Stephen’s sister, Hazel, retraces the family tree and sits down with Cass and Georgie, both adults now with children of their own, to reflect. This is an Atonement-like novel about the messy stuff that is family life: distant relatives, inheritance, memory and half-told truths. It’s about what and who we choose to remember, and the things best left in the past. Besides, as Hazel soon realises: ‘You could never find out everything.’