the group recover in their crew quarters, Steg explains that he is on a mission to find a shape-shifting Rutan spy. The Sontarans tracked the Rutan to space station Alpha, Tiger Moth's last port of call, so they are now searching every vessel that left there recently. Although Steg claims that he will leave the humans in peace, Kurt warns Lisa that the ruthless Sontarans will destroy the Tiger Moth. Robar, unaware of the Sontarans on board the Tiger Moth, has been working on the ship's power units to resolve the fluctuations. He discovers the cause to be the energy-dependent Rutan spy, who kills Robar and adopts his human form. It then kills a Sontaran trooper sent to find Robar, and attempts to escape in the Sontarans' assault craft, but Lieutenant Vorn discovers the disguised Rutan and fires at it, injuring the Rutan and forcing it to retreat. Vorn reports this to Steg, who orders a thorough search of the power room, where the Sontarans find the dead trooper and Robar's partially dissected body. Steg shows this to Lisa, encouraging her to help him destroy the Rutan, and she agrees if Steg leaves her crew and ship unharmed. Steg promises to do so, but he secretly intends to destroy the Tiger Moth as per his duty. When Lisa briefs the rest of the crew on the situation, Kurt is still suspicious, so Zorelle – fearing that Kurt's resistance could endanger her own life – tells Steg about Lisa and Kurt plotting to kill him. Steg gives his blaster to Kurt and tests him to use it. Kurt suspects a trick and does not fire, but Nikos takes the blaster and tries – only to learn that the blaster was not primed, and Steg kills him. Mari goes berserk and has to be sedated, leaving just Lisa, Kurt and Zorelle to help the Sontarans hunt the Rutan. After they leave Mari in the crew quarters, the Rutan kills her, and inhabits her body to kill Zorelle too when she returns. Lisa and Kurt kill Vorn and the remaining troopers, then confront Steg at the airlock. Kurt is wounded by Steg, but Lisa guns down the commander, who salutes her as a worthy enemy. The Rutan arrives in Zorelle's ghostly form, and vows to leave Lisa and Kurt unharmed, before entering the assault ship to escape with the secrets it learned. Steg