Mark and Seth return for the conclusion to this Tom Baker classic!

The Doctor and Leela enact a desperate plan to stop a murderous alien scout before it calls an army of its kind to lay waste to the entire planet!

Reference material used

* Official BBC site with scans of the original paperwork* Shannon Sullivan’s entry in A Brief History of Time (Travel)* TARDIS Data Core entries for the TV story as well as the novelisation* A Minecraft server dedicated to Doctor Who constructed the lighthouse