Wrth i'r Ail Ryfel Byd ddirwyn i ben, rhaid i forwr ar fwrdd llong ar Gefnfor India wneud ei ddyletswydd. Rhaid cadw gwyliadwriaeth, sganio'r gorwel am grefft y gelyn a llwybrau swigod torpidos marwol, a lansiwyd gan longau tanfor llechwraidd. Wedi'i boeni a'i greithio gan wrthdaro a cholli cyd-longwyr, tasg ein morwr yw'r Gwylio Ganol, neu oriawr y fynwent, fel y mae hen forwyr yn ei alw. Ond, wrth iddo fynd o gwmpas ei ddyletswyddau, yn oriau mân y bore, mae ei drefn yn cael ei chwalu gan gyfarfyddiad a allai roi hwb i gydbwysedd ei gyflwr meddwl bregus.
As World War Two draws to a close, a sailor aboard ship on the Indian Ocean must do his duty. Watch must be kept, the horizon scanned for enemy craft and the bubble trails of deadly torpedoes, launched by stealthy submarines. Haunted and scarred by conflict and the loss of fellow shipmates, our sailor's task is the Middle Watch, or the graveyard watch, as old mariners call it. But, as he goes about his duties, in the small hours of the morning, his routine is shattered by an encounter that could tip the balance of his delicate state of mind.
