Knights from a parallel universe arrive on Earth to find the legendary sword Excalibur. Only the Doctor and Ace, with the assistance of Brigadier Lethbridge-Stewart, can save the Earth from total catastrophe.
| Actor | Role |
|---|---|
 Sylvester McCoyThe Doctor | The Doctor |
 Sophie AldredAce | Ace |
 Nicholas CourtneyBrigadier Lethbridge-Stewart | Brigadier Lethbridge-Stewart |
 Jean MarshMorgaine | Morgaine |
 Angela BruceBrigadier Winifred Bambera | Brigadier Winifred Bambera |
| MMarek AntonThe Destroyer | The Destroyer |
| LLing TaiShou Yuing | Shou Yuing |
 Marcus GilbertAncelyn | Ancelyn |
 Christopher BowenMordred | Mordred |
 James EllisPeter Warmsley | Peter Warmsley |
 Angela DouglasDoris | Doris |
| NNoel CollinsPat Rowlinson | Pat Rowlinson |
| JJune BlandElizabeth Rowlinson | Elizabeth Rowlinson |
 Robert JezekZbrigniev | Zbrigniev |
| PPaul TomanyHusak | Husak |
 Dorota KwiatkowskaLavel | Lavel |