Tabitha is NOT Victor's sister. Tabitha was Victor's mother in her previous life. She was born after Victor's mother died that night, the same year. This is why she got those visions when she hugged Victor and why she freaked out when she watched her own past life death when Smiley got her by the tree. We still don't know where Victor's sister ended up yet. Maybe Miranda pushed her through the tree and she got stuck somewhere nothing us clear about Eloise. But it's clear now that Tabitha was Miranda in her past life and why she gas such a motherly connection to him even though he is much older than she is. She made the same bracelet as Miranda with the same mistake in the knots, she liked the same song as Miranda and she had the same visions of this place and recognizes ot from her past dreams.

Was the corpse wearing a kimono? I don't think it's Elgins visitor's corpse chained to the wall in the root cellar.

That was Victor's hiding spot with his mother and sister. His sister's bost was never found perhaps it was his sister hidden behind that doorway? Even still, that corpse appears to be older than Eloise was when she went missing.