Spain, 1936. An officer and five volunteers of the International Brigade have been ordered to cover the retreat of the battalion which, out of ammunition, is forced to move back behind the Ebro. A signal proclaims that the order has been executed, and recalls the volunteers to the rallying point. Here they find their officer mortally wounded. He orders them to fight their way through the Sierra, which is occupied by the enemy, up to the Ebro. His last instruction is "Keep together and you will live". The film traces their ordeal against almost insurmountable odds - heat, absence of water, enemy attack, and the inlying danger of disunity through their own suffering and distress. Award: Best Script, Czechoslovak Festival.