Missy tricks Clara into setting off an alarm and then handcuffs her to the wall as bait for the approaching Dalek, so that she can puncture its casing for the decaying Daleks to attack it as revenge for being abandoned.
Missy tricks Clara into setting off an alarm and then handcuffs her to the wall as bait for an approaching Dalek. She then repeatedly punctures its casing for the decaying Daleks to attack it in retaliation for being abandoned.