September 2006. The polar schooner Tara begins an extraordinary journey across the Arctic Ocean. Once the boat is anchored on the ice floe north of Siberia, the researchers of the European Damoclès program seek to answer a vital question for the future of the planet's climate: can the Arctic ice cap ever disappear? What would be the consequences of the melting ice in this region, considered the heart of the climate machine? Climatologists have long sounded the alarm: all simulations predict the complete disappearance of ice in the Arctic Ocean during the summer. The only remaining question is when.