Little Joe follows Alice (Emily Beecham), a single mother and dedicated senior plant breeder at a corporation engaged in developing new species. She has engineered a special crimson flower, remarkable not only for its beauty but also for its therapeutic value: if kept at the ideal temperature, fed properly and spoken to regularly, this plant makes its owner happy. Against company policy, Alice takes one home as a gift for her teenage son, Joe. They christen it ‘Little Joe.’ But as their plant grows, so too does Alice’s suspicion that her new creation may not be as harmless as its nickname suggests.