In the first lines, Ted Hughes refers to Sylvia Plath's temples, where the electrodes for ECT are placed, as "the tender place". The word "tender" reveals the fragility and delicacy of this place or even of her body as a whole. The electro shocks contrast harshly with the place where they are given, already suggesting the brutality of it all.
As the speaker carries out an experiment to see the effect of electricity of a twelve-volt battery on a file, he states that "it exploded like a grenade". This hyperbole brings across very efficiently that the speaker is amazed at how powerful these small electro shocks can be and makes the reader question what destructive effect it then could have on a brain when it is more powerful. Other very powerful images are similarly used by Ted Hughes to bring across what he imagines is happening in her brain, merely, violent explosions, burning and pain. The fact that he states "they" did it, suggests a desire to condemn these characters. This is also brought across in the fifth and sixth line through the repetition of "Somebody", as if he wished he could use names, showing the frustration of not being able to do so:
"They crashed The thunderbolt into your skull"
The doctors' carelessness is brought across in the tenth and eleventh line. He suggests that they were not concerned about her as a person, but simply about whether her teeth were still whole. Ted Hughes cleverly mentions the teeth to inform the reader that losing her teeth was truly possible, adding to the horror of ECT and making it seem insanely brutal: