Is it really just a figment of her imagination or has her friend really become her worst enemy?

Tiphaine and Sylvain live next door to Laëtitia and David. They're all the same age, share the same interests, and have the same vision of life. They become inseparable, a deep bond soon strengthened when both couples welcome two little boys into the world. Maxime and Milo grow up together like twins.
But this idyll is violently shattered the day Laëtitia witnesses a tragic accident that takes the life of young Maxime, Tiphaine and Sylvain’s son. From now on, their relationship will never be the same and their closeness takes on toxic aspects.