All 3 Uses of

labyrinth
in
The Scarlet Letter

But Hester could not resolve the query, being herself in a dismal labyrinth of doubt.†
p. 92.3 *

Thus Hester Prynne, whose heart had lost its regular and healthy throb, wandered without a clue in the dark labyrinth of mind; now turned aside by an insurmountable precipice; now starting back from a deep chasm.†
p. 153.6

Hester's strong, calm steadfastly-enduring spirit almost sank, at last, on beholding this dark and grim countenance of an inevitable doom, which at the moment when a passage seemed to open for the minister and herself out of their labyrinth of misery—showed itself with an unrelenting smile, right in the midst of their path.†
p. 229.1

Definitions:

(1) (labyrinth)
a maze (a complex system of paths or tunnels in which it is easy to get lost)

or (figuratively): anything so complicated that it is extremely confusing

The word "labyrinth" comes from the name of the maze of passages where, in Greek mythology, Theseus had to escape from the Minotaur.
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

Less commonly, labyrinth can refer to a complex anatomical system of interconnecting cavities -- especially the inner ear