As Peri begins to adjust to life on the TARDIS, the Doctor plays a simulation program of two species evolving, represented by black and white pixels, with the goal being to help them find evolutionary stability without harming the other. Unfortunately, the Doctor is unable to solve it. Because it's using so much memory, he plans to take it to the Proofrock-Mills Intelligence Museum in the year 3009. After Peri goes to bed, he travels to the museum in 3010, to see the program in its exhibit. When he finds the exhibit, he is amazed to see it has been solved, the program now being a swirling mass of grey. Wondering how this has been achieved, the Doctor checks the visitor's book. Most of the entries are what he expected. However, the final entry is the one that surprises him. "You won't find