Sinister Stepsister is a 2022 Lifetime Movie of the Week Thriller, directed by John Murlowski and written by Adam Rockoff.
Nice Guy dad Jeff Mitchell (Matt Pohlkamp) finds out that he fathered a previously-unknown daughter named Carlee (Annika Foster) with his high school girlfriend. She comes into his life after her mother's death. While Jeff and his wife Lisa (Jhey Castles) accept Carlee into the family, and their young son Noah (Dayne Jarrah) bonds with her, their teenage daughter Ella (Tu Morrow) notices some strange behavior from Carlee, and begins to wonder if there's more going on than it seems.
The movie also stars Johan Gran, Jacob Taylor, and Ari Atken.
Tropes for the film:
- Alliterative Title: Sinister Stepsister. Also a Rhyming Title.
- Antagonistic Offspring: Carlee grows increasingly hostile toward the Mitchell family, making Jeff worry about his family's safety with her around.
- Cool Big Sis: Carlee tries to position herself as this for Ella and Noah, in particular playing the Big Sister Instinct card when she confronts a gang of bullies who've been harassing Noah.
- Cute and Psycho: When she's not threatening or killing people, Carlee is friendly and sports a warm smile.
- Deadpan Snarker: Ella, who's immediately suspicious of Carlee and constantly rolls her eyes at her and the rest of the family's uncritical acceptance of her.
- Doppelgänger: Mentioned by name when Ella confronts Carlee about Ryan seeing her sneaking around outside the house, while Carlee lies and says she was inside all night. Noah jokingly suggests Ryan saw Carlee's doppelgänger.
- False Rape Accusation: When Ella's boyfriend Ryan catches her in a lie, Carlee accuses him of attempting to sexually assault her in order to break Jeff and Lisa's trust in him.
- Friendly Enemy: Jeff's work colleague Blake. He's a bit cocky and Jeff is rightfully upset at losing out on a promotion to Blake, despite him putting in twice as much work. Despite this, the two are incredibly civil towards each other and Blake reveals that he genuinely respects Jeff's knowledge as a contractor.
- I Just Want to Be Loved: The Motive Rant Samantha delivers at the climax establishes this as the reason she killed Carlee and stole her identity—Samantha spent her childhood bouncing between foster homes, and hearing Carlee's story about locating her father awakened Samantha's deep desire to be part of a loving family.
- I Never Told You My Name: Carlee calls Jeff by his name when they first meet, to his confusion, which leads to her revealing that he's her father.
- I Will Punish Your Friend for Your Failure: Carlee threatens to kill Ryan's family if he doesn't stay away from Ella and stop trying to expose her lies.
- Luke, You Are My Father: Carlee approaches Jeff at a bar and reveals herself as his long-lost daughter. He really did have a long-lost daughter named Carlee Byrne, but the woman who introduces herself as Carlee is actually Samantha Ridge, who killed the real Carlee and stole her identity.
- Missing Mom: Carlee's mom has died, prompting her to search for her father and find out the truth about her family history.
- Never Trust a Title: Despite the title, Carlee is actually the half-sister of Ella and Noah. Or at least is pretending to be one.
- Only Sane Woman: Ella realizes from the start that Carlee's story somehow doesn't add up, even though the rest of the family buys it.
- Pop-Up Texting: Used when Ella and Ryan text each other.
- Self-Plagiarism:
- In several ways this is a retooled version of Lifetime's earlier Psycho Daughter (starring Sydney Sweeney in the title role), right down to the villain's real first name being Samantha.
- Lifetime's A Deadly Grudge, which debuted about two months before this movie, has an identical premise (a kindly father suddenly meets his previously-unknown daughter from an earlier relationship, she integrates herself into the family, but her half-sister becomes suspicious of her), and Annika Foster co-starred in both films (she's the suspicious heroine sister in A Deadly Grudge, while she's the evil sister here).
- Theme Naming: The Mitchells (Jeff, Lisa, Ella, Noah) all have first names with four letters.
- Trademark Favorite Food: The Mitchells order pizza on no more than three separate occasions throughout the movie.
- Villain: Exit, Stage Left: It's actually the setup for the climax rather than after the climax, but when the Mitchells discover the very incriminating presence of Blake's wallet among her belongings, alongside her real DNA test results, Carlee first tries to fumble her way through an I Can Explain gambit, but suddenly realizes it's not working, so she just bolts out the door.
- Would Hurt a Child: Implied. When Noah uncovers evidence proving that Carlee is lying about who she is and was responsible for Blake's death, a scowling Carlee corners him in her room and starts making threatening statements, suggesting she was willing to hurt or even kill the young boy to keep him quiet. Thankfully, Ella arrives just in time to distract her before she can go any further.
- Wounded Gazelle Gambit: How Samantha Ridge murdered Carlee Byrne—she laid down motionless between some bushes while the other woman was on a jog, making her think she was unconscious, or possibly dead, then attacked her when she tried to help.
