At the beginning of the 22nd century, the sky of the Earth is clouded with darkness, fraught with confusion and suffering. From distant stars, a dangerous threat in the form of the Esterai Empire is approaching Earth. A terrible enemy from the center of the galaxy plans to use biological weapons like never before. Earthlings fly away in search of a new home, but migration will not save them from interstellar war. Young Roma Nikitin decides to become a member of the resistance to the alien invader and enters the Military Academy to study as an intelligence officer. In the life of cadets - boys and girls who have just crossed the threshold of adulthood, there is a place for everything - studies, parties, dates, fights, space flights, friendship, enmity, love, betrayal. They will plunge into the world of adventures of youth. But time is inexorable. The merciless Esterai Empire has plans for enslavement and weaves obscure intrigues against the Earth. In the impending war, the young children of spring will only have to turn into winter soldiers and use all their strength to survive.