Perfect Roast Potatoes concerns the strained relationship between two estranged British siblings - quirky, delusional Tamara and her uptight, refractory brother, William. Tamara wakes on Christmas morning to find her ailing mother, Mugsy, has passed away in the night. Unhinged by the loss, Tamara coerces William to agree to Christmas dinner as planned - corpse and all - and she obsessively sets out to recreate the perfect roast potatoes Mugsy made every year. Tamara slowly dissolves as batch after batch fails to meet muster until William intervenes, helping her to accept what's happened and make peace with imperfection.