Daddy, I have had to kill you. You died before I had time – (lines 6-7)
Here we get our first paradoxical look at mortality. It's not possible to kill someone who's already dead, but you can count on our speaker to try. These lines reveal the core of this poem – the speaker's father died, and she still hasn't coped with it.
A Jew to Dachau, Auschwitz, Belsen. I began to talk like a Jew. I think I may well be a Jew. (lines 33-35)
Here, the speaker references concentration camps, where millions of Jews died during the Holocaust. She is so distraught in the face of her dead father's memories – especially the memories of his German characteristics – that she feels like she's a Jew in the Holocaust, on her way to a tragic and mass death.
I was ten when they buried you. At twenty I tried to die And get back, back, back to you. I thought even the bones would do. (lines 57-60)
These lines show us explicitly that the speaker's father's death led to an attempt to take her own life. She thought that, when she was dead, she could be with her father again, even if just her bones were close to his bones. Death is desirable for the speaker. She longs to know the boundaries of her own mortality.
But they pulled me out of the sack, And they stuck me together with glue. (lines 61-62)
Rather than showing us more of this speaker's obsession with death, these lines demonstrate the resilience of life. Unfortunately for our speaker, it's not a happy life that she's restored to. She feels like she's been pulled out of a sack and stuck together haphazardly.
If I've killed one man, I've killed two – (line 71)
We can guess that the speaker didn't kill her father – after all, she was only ten when he died. It also seems unlikely that she killed her husband, who is the second victim referenced here. But this line finally shows our narrator as the wielder, and not the victim, of mortality. Perhaps she'd prefer to have killed her father rather than to think of him as passing away as a result of something she can't control.
Daddy, you can lie back now
There's a stake in your fat black heart (lines 75-76)
These lines treat death as a form of relaxation – the father can lie back in his grave now that he's been killed again. But this is no ordinary death – it's vampire death. The father is already dead, but has refused to die in the mind of our speaker. So she has to kill him as if he is a vampire, by putting a stake in his heart. But he can lie back now that he is dead, and leave his daughter alone.