Poppy's Killer is the assailant that confronted and murdered Poppy Saybrook, staging it as a suicide and later threatening her cousins.
Poppy's Killer had possibly followed but confronted Poppy as she arrived at her office fairly early in the morning inside Saybrooks' Diamonds, the family company. Poppy was later pushed or thrown before 7:05 A.M., as that is where her body was on the ground. The killer then faked a suicide note, finishing two minutes later at 7:07 A.M. “I just can’t handle it anymore,” it read. “I’m sorry. Good-bye.”
During a dangerous confrontation on the bridge, Julia revealed herself as the murderer of both Poppy and Steven. She explained that she killed Poppy because she knew a secret about the Saybrook family, and planned to reveal it. Julia, desperate to be apart of the family and earn her spades with Mason, killed Poppy to protect him and his company. She was also furious with Poppy and Penelope, as they got everything that her daughter, Danielle, was supposed to have. Danielle was never properly claimed by Mason, and thus, wasn't part of the Saybrook legacy and fortune which infuriated Julia and lead her to the murdering.
In the end, the FBI arrived and shot Julia, who fell off the bridge and into the water and died.