The one where a Sontaran does some experiments...
Elisabeth Sladen plays her first scene with Styre really well, selling Sarah's shock and fear of what she thinks is a creature she'd seen the back of. Kevin Lindsay is just as menacing as Styre as he was Linx (perhaps even more so), exemplified by his gradual, silent approach to Sarah before grabbing her by the thorax. Sadly, the mask for Styre isn't as effective as it was for Linx, with obvious loose holes for the eyes, and a less realistic, rubbery skin lacking the detail of The Time Warrior's version (I miss the little hairs). The fact Styre's lower lip is attached to Lindsay's jaw means you can quite clearly see the actor speaking inside, which also unravels the illusion.
When poor Roth takes his chance to escape, Styre guns him down in cold blood, having already got from him all of the scientific knowledge he can muster. Roth was of no more use to him, so he killed him. "I am a warrior," Styre justifies. "Murderer. MURDERER!" shouts Sladen. Electrifying stuff.

