Harry dozed fitfully, sinking into dreams full of clammy, rotted hands and petrified pleading, jerking awake to dwell again on his mother's voice.
Harry potter and the prisoner of Azkaban
Harry is having a nightmare of his dead mother. So I guess the part marked in bold means something similar, but don't know what exactly it means.
It's hard to understand this phrase because I don't know why "to" is used here(grammatical role of "to" maybe?), and also because of "dwell on ~".
Does this mean Harry suddenly woke up, because of her mother's voice?