Unfortunately, Robin had somehow lost his passport and feared being deported.
Robin and Colin decided to spend a night in the abandoned Frankendael crypt, having arrived a day early, and found no room at the hostels. Colin was abducted by the Ergon and Robin escaped, later getting help from Colin's cousin Tegan Jovanka. They returned to the mansion only to be captured themselves, but were freed by the Fifth Doctor. (TV: Arc of Infinity)