平凡的一家人阿文(陈以文 饰)和琴姐(柯淑勤 饰)育有两个儿子,叛逆的小儿子阿和(巫建和 饰)与好友菜头(刘冠廷 饰)砍伤人进了少年辅育院,但阿和的女友小玉(吴岱凌 饰)却带着身孕来家里…琴姐不顾阿文反对,将小玉留下来照顾。此时,被砍伤者家属也来找阿文求取巨额赔偿,阿文受不了总是带来麻烦的小儿子,将所有希望都寄托在资优生大儿子阿豪(许光汉 饰)身上,却不知道温暖善良的阿豪心中也藏着不为人知的秘密…A Sun follows a troubled family of four. A-Ho, the younger son, has always been a problematic child, and his father, A-Wen has invested all his hopes and expectations in his introverted eldest son, A-Hao. While A-Hao is trying to get into medical school, A-Ho faces juvenile detention for a crime committed with his best friend - although not entirely of his own will. A-Wen abandons A-Ho, refusing to help and even requesting the judge to sentence his son as harshly as possible. Not long after A-Ho is sent to prison, to make matters worse, his girlfriend shows up on his mother Qin's doorstep. The teenage girl is pregnant and determined to have A-Ho's child, even though he is locked up and has no idea she is expecting.