All 3 Uses of

theme
in
Dracula

The foolhardiness or ignorance of her officers was a prolific theme for comment whilst she remained in sight, and efforts were made to signal her to reduce sail in the face of her danger.
p. 86.6

theme = recurring idea

I thought I would find out if his apathy were real or only assumed, and tried to lead him to talk of his pets, a theme which had never failed to excite his attention.
p. 111.8

theme = basic idea

If I do, or if I even open this again, it will be to deal with different people and different themes, for here at the end, where the romance of my life is told, ere I go back to take up the thread of my life-work, I say sadly and without hope, "FINIS".
p. 188.6 *

themes = basic ideas

Definitions:

(1) (theme as in: theme of the novel)
a basic idea that underlies what is being said or done -- especially in a literary or artistic work
(2) (theme as in: musical theme)
the initial or primary melody of a musical composition

or

(as in "theme song") music that is most repeated in a film, television series, or other theatrical production
(3) (theme as in: wrote a 2-page theme on my summer)
an essay written by a student

(This sense of theme is much rarer in recent decades than in the past.)