After Lola's miscarriage on her wedding day, she and her husband adopt orphaned twin siblings, Tin and Tina. However, the twins soon begin to exhibit strange and disturbing behavior, all influenced by their strict upbringing at the convent. Slow-burning and atmospheric, Tin & Tina uses the "evil child" trope to tackle the horrors of orthodox Catholicism and motherhood. While it does deliver on the bare bones of the conversations, the continuous disbelief that follows the provable, horrendous actions becomes tiresome. There is mention of Lola growing up in a convent, and the couple's insistence on not having a disabled child (even though Lola is disabled) creates more discussions that are never finished. Neither the story nor the scare is memorable enough.

Milena Smit, as Lola, excels in her role. She embodies the exhaustion, turmoil, and doubt as a wife and mother struggling to perform in the roles expected of her. Smit delivers, from her pensive observation of the twins to her impassioned rejection of their dangerous and unyielding devotion to religion. Lola's languishing under the pressure of motherhood and womanhood is easily the most compelling part of the film.