Still on the run with the Daleks' taranium core, the Doctor, Steven and Sara land on a beautiful, flower-covered asteroid orbiting a pair of twin gas giants. Then they're rudely interrupted by a squad of the Space Security Service soldiers battling a strange, squat group of warlike aliens - the Sontarans.
Chronologically, this is the last story of the "Daleks' Master Plan" interquels. It finishes with the TARDIS team detecting the Monk's TARDIS, leading into Episode 8, "Volcano". Because it's the Doctor's first ever meeting with the Sontarans, it's named after them as though it were a Sixties serial.
Tropes:
- Blue-and-Orange Morality: Brought up as part of the trouble when Steven is being interrogated by the Sontarans, as for them the idea that he would tolerate being held prisoner for years rather than kill himself makes no sense.
- Even Evil Has Standards: Ultimately Sara is able to convince the Sontarans to let the refugee fleet through by making it clear that the larger ships have no weapons.
- Out of the Inferno: At one point a Sontaran walks through a lava flow because his armour is durable enough to endure the heat.
- Timey-Wimey Ball: Sara is aware of the events of this crisis from her future knowledge, leaving her uncertain about how this should affect her response to the situation.
- Whole-Plot Reference: The premise is straight from The Guns of Navarone, with a mission to destroy a Sontaran space-gun before it blows up a convoy. There's even an occupied village.
- Worthy Opponent: Invoked; when Sara helps a Sontaran see that the advancing fleet is just refugee ships protected by smaller craft, the Sontaran acknowledges the nobility of the smaller fighters sacrificing themselves to save the larger ships and shuts down the cannon.
