In the year 2961, the time is after humanity and nature has recovered the land. A hunter named Cygnus is called to rise above his duty. He provides for Last Arc, a once nomadic band of survivors in need of food and water that is now growing scarce. The answer must be found before a group of outlandish Heretics descend upon them. Cygnus must voyage across the treacherous landscape to defend his people. Sent by Nova, the matriarch of the band, she acts based on her vision for Cygnus to find a seed of hope. The future of Last Arc is for him to discover, Cygnus ventures into a hostile landscape in search of an answer for his people. On this journey of encountering many traps and dangers, Cygnus discovers what has been hunting him is his identity.

　　威克斯教員帶著他剛完成中學學業的學生們修學觀光。

　　梧桐中學高二十八班是遠近聞名的問題班級，后進生、藝術生、體育生、不良少年聚集在此，以宋宸（柯焱曦 飾）為首的男生幫派和以秦淼淼（熊婧文 飾）為首的女生幫派互相不服，班級混亂無序。一天，高二十八班收到了一封信，這封信自稱是由一年后的他們集體寄來。信上說，即將調來的班主任譚 睿明（秦海 飾）會改變十八班，成為對他們最重要的人。然而在一年后的未來，譚老師卻永遠地離開了他們。為了實現一段沒有遺憾的青春，扭轉歷史，少年們決定按照信上所說，挑戰一個個不可能實現的任務...

　　Follows a man whose pregnant wife gets murdered and despite the police investigation, the truth is unknown. He tries to find what happened, which confronts him with situations of suspense and terror.