Noua and his grandfather, sitting on a bench in a small square, tell jokes and share their love for mathematics and life. Everything is familiar and strange at the same time, because this "square" is slowly shrinking as the grandfather's memory fades. The connection with his grandson and son and the love for his wife, who is no longer alive, help the grandfather to stay in the "square" and fight against dementia.
A small but precious book about old age, the incomprehensible diseases of the brain, and the difficult moments we live through when we say goodbye to someone while they are still among us. But more than anything, it is a book about the ability to laugh out loud, to hug tightly, and to appreciate the value of a beautiful balloon traveling towards the sky, while there is still time.