Leap Year Killer

Nina Guerrero is the one who managed to escape from the mysterious serial killer known as Cipher, and then eliminate him. Now she is part of a group of profilers at the FBI. …Mother, father, and newborn daughter — all... dead. The eight-day-old baby was asphyxiated, the man was shot in the heart, and the woman lay in the bathtub and shot herself in the temple. It all looks like a double murder and suicide. But it’s not.
This is the signature of a new serial killer. Or is he new? Nina Guerrero and her colleagues from the Behavioral Analysis Unit quickly find out that he has been on the hunt… for 28 years. He kills across the country, and each crime scene resembles the terrifying legend of La Llorona – the ghost of a weeping woman. A legend that frightened Nina in her childhood when she was a defenseless child.
The staging is so good that no one has yet thought to connect these cases together. 
And the strangest thing is – the murders occur every leap year, on February 29…