Takes place between Journey's End and The End of Time. The Chelsea Flower Show is hardly the most exciting or dangerous event on the calendar, or so the Doctor thinks. But this is Chelsea 426, a city-sized future colony floating on the clouds of Saturn, and the flowers are more than they seem. As the Doctor investigates, he becomes more and more worried. Why is the store owner, Mr. Pemberton, acting so strangely? And what is Professor Wilberforce's terrible secret? They're close to finding the answers when a familiar enemy appears and the stakes suddenly become much higher. The Sontarans have their own plans, and they are not here to arrange bouquets...