After offering a kidney to her sister they discover they were both adopted. They go on a search for family and a kidney based only on their Mum’s old diary.PS Adoptive parents are dead, can’t see how to fit that in.
How about this:
“Two sisters discover they’re not related when one attempts to offer the other a life-saving kidney. They search for their real family guided only by notes in their dead ‘mother’s’ diary.”
Or something along those lines…
Switch it. A dead Kidney donor is found to be an exact match for her recipient, meaning they were twins. The recipient must go on a detective hunt to find out how and why they were separated, and the search leads her across continents and through some of the twentieth century’s most tragic history.
Does it have to be a dual protagonist plot?
This sounds like a family drama and feels best told from a single point of view, either the sister trying to save or the sister trying to survive.
It has a nice built in ticking time bomb and high stakes so well done on that but it sounds like it has two goals. One goal to find their real parents the other to find a kidney I personally find the later more interesting. The stakes are higher and the time is running out, why would they care abut a mother they know nothing about when life is at risk?
The search for the real parent could work as a sub plot but it shouldn’t distract from the ‘A’ plot of saving her life and in as such has no place in the logline.
Hope this helps.