Five architects compete for the approval of architecture-obsessed Chicagoans in the contest to build the city's new public library. NOVA looks at the strengths and weakness of each of the surprisingly varied entries.

England, 1883. The Doctor brings Ace to a house called Gabriel Chase in her home town of Perivale. The Gothic mansion is presided over by one Josiah Samuel Smith - an evolved alien brought to Earth in a stone spaceship that is now in the basement beneath the house, and which still holds an ancient evil capable of wiping out the world.