Three Legs Good (S03E05)

Rosemary and Laura are in the midst of re-planting the historic Regent's Park when their efforts are thwarted by a series of plant thefts right after they’ve been planted. As they investigate the thefts, things take a dark turn when they discover the body of an Eastern European doctor, shot dead while out with his three-legged dog. As they dig deeper, the duo uncovers hidden secrets within the park and start to suspect that the doctor may not have been the true target, especially when his colleague, who owns the dog, becomes the next victim of a shooting.