Jane Fisher was Phryne's sister who disappeared. The disappearance haunted Phryne for years.
Jane was born September 21th. Due to that her father was drunk at the time he registered her birth he wrote Phryne's birthdate, December 21th, on Jane's certificate instead. That mistake was that got her killed. Murdoch Foyle was searching for girls who shared his birthdate (December 21th) to be his four goddess that would protect him for his journey to the afterlife. Through an old student who worked at the office for birth, marriage and death, he got access to the birthcertificates and selected his four victims from the neighborhood from the university where he worked. During a circus performance that Jane and Phryne were watching Jane vanished. Her body was first recovered years after and was buried in the family plot.