Claude Opus 4.8 vs GPT-5.6 Terra for book writing

The letters shouldn't exist.

They arrive addressed to Edith Brand's sister — dead for forty years — postmarked from a village that no longer exists, drowned beneath a reservoir since 1971.

Retired and haunted, Edith returns to the place she once called home, renting a room above the pub from a landlord whose memory runs deeper than the water. But the further she wades into the past, the murkier her sister's death becomes. Was it an accident? A tragedy of her own making? Or something darker, long buried?

Some secrets don't stay drowned.

And…

When retired lighthouse keeper Edith Brand receives letters addressed to her dead sister, she is drawn back to the village where they grew up—though it has lain beneath a reservoir since 1971.

Renting a room above the pub, Edith finds old memories stirring and old secrets guarded fiercely. The landlord remembers more than he admits, and the circumstances of her sister’s death begin to look disturbingly unclear.

Was it an accident? Suicide? Or something someone has spent forty years trying to keep submerged?