'This bed's horrid', says Violet Elizabeth, as story intensifies (3,4,8)
I believe the answer is:
the plot thickens
'story intensifies' is the definition.
(phrase describing a plot becoming more complex)
'this bed's horrid says violet elizabeth' is the wordplay.
I cannot quite understand how this works, but
'bed' could be 'plot' (a bed or plot of soil) and 'plot' is found in the answer.
This explanation may well be incorrect...
'as' is the link.
(Other definitions for the plot thickens that I've seen before include "things get less clear" , "When broader nib is used on graph paper" .)