The actors star as a pair of new lovers who break into houses over a holiday weekend in Joy Wilkinson’s debut feature.

Harking back to those erotic thrillers of yore, especially from the 1980s and 90s, writer-director Joy Wilkinson’s 7 Keys, her debut feature, starts out full of promise and potential — much like the impromptu hook-up that gets the plot rolling. Unfortunately, like many an ill-starred love match, what follows is disappointing as things evolve in a lurid and yet strangely predictable direction. But while it all goes sour and south in the last act, there are definitely sparks of originality in the early running, supported by a brace of strong performances from Emma McDonald and Billy Postlethwaite, who deserve better than what the script gives them to work with.

McDonald and Postlethwaite aren’t entirely unknown quantities. The two worked with Wilkinson before on a short film, The Everlasting Club, while McDonald had a supporting role in Layla, which premiered in Sundance last January. Postlethwaite, who is the son of the late Pete Postlethwaite (In the Name of the Father), has been slightly more visible, appearing recently in Indiana Jones and the Dial of Destiny while his resume is full of small roles on some of Britain’s most talent-hungry, TV-show training grounds, such as Midsomer Murders and Game of Thrones. Of late, he’s moved up the pay scale with recurring roles in various lesser-known series (Beforeigners, Silo, The Winter King).

So far, so meet cute, although the script soon adds a dollop of darkness in the way Lena stalks Daniel home. Somewhere between the first kiss on the couch and the first bout of shagging in the bedroom, Lena notices that Daniel has a great number of keys on a keyring, not because he’s a concierge or a security worker, but because he’s kept the front door and main door keys to every place he’s lived in London.

A bit of a tearaway herself, raised by a single mother on a low income, Lena suggests they visit each of the properties. The aim is not to steal anything, just to break in, leave almost no trace, and snoop around. Because it’s a bank holiday weekend, many folks will be out of town, Lena reasons, and so Daniel, who gets more confident by the minute, agrees. What could possibly go wrong?

Lots, as it turns out. Neither party is exactly who they seem to be, but the ultimate reveal as to which of them is the more damaged and dangerous is not that much of a surprise. But up until the fun starts to drain away from the weekend like blood from a corpse, the two actors have genuine chemistry, and production and costume designer Natasha Jenkins does a bang-up job of sketching what each of the residents of the apartments they visit is like just with props and styling details. At its best, 7 Keys evokes the variety of Londoners and London neighborhoods, even if it’s frustratingly evasive about the geographical details of where each apartment and house are located.