Cold case

[Gibbon]

Plot twist - surviving descendant is married to long lost twin sister, lady doesn't discover this until after the stabbing. Twin sister catches her in the act, then helps her as her husband has been violent with her over the years of their marriage.

I wondered who could be behind the tulipe plot of 'Playing Nice'.

[xoggoth]

Or all descendants of The Ripper go round stabbing people but are acquitted of murder on the grounds that the tendency is genetic so not their fault.