Rosemary and Laura are re-planting historic Regent's Park, which is hampered when they find plants being stolen shortly after being planted. While trying to determine who is stealing them, they soon find themselves dealing with a murder when an Eastern European doctor is found shot dead, while walking a three-legged dog. It's not long before the pair unearth secrets in the park, and begin suspecting the doctor might not have been the intended victim, when his colleague, the dog's owner, is soon shot themselves...