A funeral in Paris' Notre Dame Cathedral is interrupted by a small, gray, uninvited woman who blithely makes her way to the coffin, lifts her veil and embraces the deceased. The congregation is aghast: Has Mademoiselle Janvier dared turn up? The woman releases the dead man and, taking an old bicycle bell from her handbag, rings it loudly, once, twice, before skipping off past the open-mouthed mourners to the exit.

So begins Swiss-born Alex Capus' European bestseller, "Léon and Louise" (translated by John Brownjohn, Haus Publishing, 265 pages, $15), a mesmerizing tale of love, longing and loyalty through the ages. After this jolting opener we go back to the summer of 1918 and the last days of World War I. French teenager Léon Le Gall falls in love with Louise Janvier. Just as their relationship is blossoming, they are wounded by German artillery fire and separated, both believing the other to be dead. We fast-forward a decade to discover Léon is now living in Paris with his wife, Yvonne. A chance encounter on the Métro one day reunites him with Louise, but not for long: She refuses to wreck Léon's marriage and so they drift apart once more, only to be completely cut off when the Nazis march into the capital. Will they meet again, and can that adolescent love ever be rekindled?

Narrated by Léon's grandson, "Léon and Louise" ushers us through turbulent times and charts the unquenchable triumph of the human spirit. Capus' leads are riveting, credible creations -- he sensible and correct, she feisty and headstrong. We root for them, especially when war takes over and threatens to sunder them for good. Capus writes wonderfully on their disparate lives and attempts to stay afloat: Louise in exile in West Africa with roguish sailors and the Banque de France's gold reserves; Léon at the Paris police headquarters reluctantly compiling lists of undesirables for the SS.

The novel is structured in such a way that we know from the outset that both characters survive the war: Léon lies dead in Notre Dame years later, and Louise gate-crashes the funeral. By rights, then, there should be no tension and few surprises. But Capus keeps us engrossed by exploring the complexities of love and consistently impresses with wry observations and neat phrasing. Léon loses Louise, returns to his wife and so becomes "unfaithful to his own infidelity." Louise ponders over love's meaning and function and decides, "Love is an imposition, isn't it? Especially when it lasts a quarter of a century."

This love-conquers-all tale could easily have been trite and saccharine, but instead Capus' fusion of gripping drama and believable characters renders "Léon and Louise" both powerful and poignant.

Malcolm Forbes has written for the Times Literary Supplement, the Economist and the Daily Beast. Born in Edinburgh, he lives in Berlin.