Sasiwimol is an extremely successful director and an open-minded mother who maintains a close and easy-going rapport with her teenage son, Wang. However, even someone as understanding as Sasiwimol is left shocked and bewildered upon learning that Wang is about to experience his first feelings of love and has fallen for the one and only Inthawut, a long-time trusted friend and contemporary of hers. In an instant, life, love, friendship and trust are all put to the test as the three souls find themselves converged by an intricate "line" that is set to forever alter the close-knit bond between a son, a mother and her beloved friend.