Isabella is the most mysterious character of the season. As a young woman who has moved around her whole life, has diplomats as parents, and lots of juicy, most likely illegal history, she is a great candidate for the murderer. In July 1999, Isabella arrived at the Landry household, hoping to start over in a small town. She immediately takes an interest in Luke, Megan’s best friend, and asks her permission if she can make a move on him. Megan initially lies about her feelings towards Luke, and Isabella and Luke kiss and hang out like a couple. As the flashbacks and fast-forwards occur, it is revealed that Megan and Luke are dating by December 1999. This is her first motive. She liked Luke, made her move, and as soon as they started getting close, Megan revealed her feelings too, and Isabella backed off. However, those burning feelings and jealousy don’t go away so quickly…
We know Isabella has a dark past because of her suspicious stories, having gone to three different schools in three years, and more unknown secrets. In episode 5, July 1999, Trevor surprises Isabella and mentions the murder of her best friend Lisa, who also happens to be Trevor’s sister, who she had been writing letters to and not sending the entire time. We find out that she drowned in St. Barts, and though nothing is made clear, it is incredibly telling of what she could be capable of. Trevor expresses, “You know Iz. She’s capable of absolutely anything”. Isabella’s lawyer also confirmed that she had had to hide something like this before, referring to Lisa’s drowning, but it was covered up because of her diplomatic immunity.
In July 2000, when Luke’s body is brought out of the lake, she immediately turns to Isabella and says they need to get their stories straight, indicating that they were involved somehow. The Sheriff also explains that her backpack was found at Luke’s cabin with a lot of money inside and her prints on the gun, though she claimed to have not been there since July 1999.
In episode 6, Megan finds the police reports that say Isabella convinced her friend Lisa to go swimming while drunk the night she died, along with the fact that she fled St. Barts overnight by helicopter after that incident.
In December 1999, Luke tried to kiss Isabella at The Plunge, even though he was with Megan, giving her more motive to kill Luke. The question is, would she kill Luke so neither of them can have him or so she can have Megan all to herself?