Li Mi (Zhou Xun) drives a taxi in Kunming. She has been looking fruitlessly for her vanished boyfriend for four years. On the same day that she picks up two passengers that turn out to be desperate criminals (Wang Baoqiang and Wang Yanhui), she thinks she sees her missing lover – only he (Deng Chao) claims to be someone else entirely.

The Equation of Love and Death has one of the more ridiculously pretentious English-language titles I have seen from a Chinese film. A literal translation of its Chinese title is Li Mi’s Supposition, which is not only less ridiculous it is also more accurate to the film itself. The film focuses closely on the titular Li Mi, who has wasted so much of her life waiting for a man that she may never see again – and when she thinks she has found him, it seems that entire wait may have been for nothing.

Narratively speaking the film is a weirdly odd mess. Early scenes are dominated by Li Mi being taken hostage by two men: the muscular, gravelly Qui Huogui (Wang Yanhui) and the weedy, credulous Qui Shuitian (Wang Baoqiang). The tone veers wildly from genuinely tense threats to a sort of ridiculous comedy of errors. Later scenes shift suddenly to address whether or not Ma Bing, a man with a very close resemblance to Li Mi’s boyfriend Fang Wen, is who he claims to be or not. In this second half Li Mi spends a fair amount of time with Ye Qingcheng (Zhang Hanyu), an ill-tempered and impatient police officer investigating both the Quis’ crimes and Ma’s identity. Zhang is rather endearing as Ye, gradually forming quite a sympathetic relationship with Li Mi without ever falling into a romantic overture.

Wang Baoqiang cuts a pathetic figure as Qui Shuitian. While his companion Huogui tries to keep their intentions secret, Shuitian keeps over-sharing every element of his life that occurs to him. When events turn violent, he’s visibly distressed. Even once he is arrested and in police custody he seems weirdly disaffected, and more interested in getting Li Mi to help him track down a long-lost girlfriend from his home town.

Ultimately, however, the film belongs to Zhou Xun. She gives Li Mi a jagged and nervous quality. She chain smokes cigarettes as a nervous tick. Her emotions seem perpetually frayed. She has obsessed over Fang Wen’s fate for so long and so ardently that it has clearly affected her not just emotionally but on a psychological level as well. Zhou makes the character hugely sympathetic and delicately multi-layered. She is a strong woman, but she is a brittle one as well. She is never anything short of rivetting. To my mind Zhou is one of China’s most interesting actresses working today, but despite a supporting role in the Wachowskis’ Cloud Atlas (2012) she has never made a huge impact outside of Chinese-speaking markets.

It is Zhou’s performance that makes The Equation of Love and Death work as well as it does. Its plot may feel a little messy, and its tone shifts a little too radically from beginning to end, but it is almost impossible not to feel for Li Mi. You want her to succeed. You want her to find peace. You want her to be happy. It’s a powerful performance at the heart of a fascinating little film.