Irish actor Eva Birthistle has given successful performances in Ken Loach’s Ae Fond Kiss, Peter Greenaway’s Nightwatching, and David Keating’s Wake Wood. Now she pivots to directing, with this interesting and worthwhile debut feature, developed from her earlier 10-minute short from 2020, entitled Kathleen Was Here, about a vulnerable adult who was once in care, returning to her childhood home after the death of a mother who still haunts her thoughts.

Birthistle extends the mood-music of this earlier piece, repurposing the memory-flashback moments, hanging it on a psychological drama-thriller plot about a disturbing cuckoo-in-the-nest, complete with an almost Joe Eszterhas-level nailbiter ending. The plot machinations required to facilitate this are maybe a bit contrived, but it hangs together, and Birthistle directs the actors strongly and sympathetically.

Hazel Doupe reprises the role of Kathleen who has returned in her late teens to the chaotic small-town home of her late mother. She is bored, depressed and listlessly obsessed with celebrities’ perfect lives. Then she is befriended by a kindly neighbour Dee (played by Clare Dunne, known for Phyllida Lloyd’s abuse drama Herself, in which she was co-writer and star). Dee is welcoming to troubled and spiky Kathleen, introducing her to her husband Rory (Peter Coonan) and young son, and soon Kathleen, in her damaged and emotionally parasitic way, goes into single-white-female-Ripley mode, becoming obsessed with Dee, and setting about splitting up her marriage so they can be together.

There are some clever moments, including Kathleen’s cunningly manipulative use of a selfie and her staging of a near car accident to make Dee’s family feel grateful to her. Perhaps the move to something more generic means sacrificing subtlety and sympathy, but this is strong and fluent storytelling.

• Kathleen Is Here is in British and Irish cinemas from 18 October