Whistle and I'll come to You (TV)

After placing his ailing wife Alice in a care home elderly academic James Parkin goes to stay at a wintry out-of-season hotel which they used to visit together. Walking on a deserted beach he finds a ring with a Latin inscription,which translates as Who Is This Who Is Coming. He takes the ring back to the hotel but at night he hears loud banging on his door,even though he is the sole guest,as well as seeing a white-clad apparition on the beach.He is seemingly the victim of ghostly revenge - but who is the avenger?