When Charles Darwin takes a break from a long sea voyage to look for shells on the Galapagos Islands, he finds two things that really shouldn’t be there. The first is a sunbathing Doctor. The second is a fresh Silurian skull... When more Silurians are discovered by Darwin’s crew – alive, this time – there is pandemonium. And when the island’s volcano starts erupting, years ahead of schedule, it looks like all-out war. The Doctor has his hands full. Can he keep Charles – and his evolutionary theory – alive?