"It had never occurred to me that our lives, which had been so closely interwoven, could unravel with such speed."
After Ruth takes Tommy from Kathy, they all move into a cottage home together years later, and Kathy cannot stand to watch and hear their relationship day in and out. So, she becomes a carer and leaves them behind and this is when she makes this statement.
"For me, the real test of being a carer is when a donor completes earlier than expected."
Kathy has gone through multiple donors that she's cared for and this statement relates to the fact that though their purpose is to give their organs to their clones, that death is not made any easier. In fact, it is equally as hard, potentially more so for her.
"And as you know, when they want to complete they usually do."
A nurse in the hospital shares with Kathy that Ruth has had two operations and is weak. She believes that she will complete on her next surgery. Not because they've harvested her organs, but because she simply would rather die than fight to live.
