The Return is a Document in the Rise of the Tomb Raider: 20 Year Celebration DLC Blood Ties. It belongs to the Lord Croft's Journals set and contains the musings of Lara's father, mostly about the funeral of his wife Amelia.
This document is located in the family crypt and can easily be overlooked. It is in the left wall alcove of the passage leading into the crypt.
Instead, as the mausoleum stone slid into place, I felt... a sort of peace and energy, one that I confess caught me entirely off guard. This was not the terminus of our story, and I was fool to think so. Her body may be gone, bit her spirit still resides here, in the manor, in me, in Lara. Her soul is forever twined with mine, and death is just... a momentary interruption. I walked out of that cold quiet into the sunlight that burned my eyes, and I have ever been more sure.Death is not the end, and there is work yet to do.