Young Cuchulainn, one of the main characters of the Irish epic, sails to the hawk spring, which flows very rarely and for a very short time. According to legend, if you drink water from there, you will become immortal. At the source he meets an old man who once, being equally young, came to the source. But he never managed to catch the right moment. And now he has already grown old, spent most of his life here, but never received immortality. The keeper of the spring appears and begins her magical dance, putting the old man to sleep. Young Cu Chulainn tries to catch up with her and misses the moment when the source begins to flow. It is this event that will determine much in his heroic fate.