Erful is a strange and lonely character, and his only happy memories are those of his school days. When a former pupil is murdered, Erful feels that he has a duty to solve the case. In doing so, he has to venture from his familiar world, and grapple with issues from his own past if he wishes to survive.

Un rhyfedd yw Erful, yn byw bywyd unig. Yr unig atgofion hapus sydd ganddo yw'r rhai o'i gyfnod yn yr ysgol. Felly, pan gaiff un o'i gyd-ddisgyblion ei llofruddio, teimla ei bod yn ddyletswydd arno i ddatrys y dirgelwch. Rhaid iddo ymdopi â'r byd tu allan i furiau ei gartref, ac os yw am oroesi, rhaid i Erful fynd i'r afael â'i orffennol ei hun.