background

bar

behind

cage

captive

capture

cell

close

conceptual

confined

confinement

convict

dark

darkness

door

empty

escape

exit

exiting

free

freed

freedom

gate

grey

idea

imprison

imprisonment

incarcerate

inside

into

iron

jail

jailbird

light

metal

nobody

old

open

opened

out

pet

possibilities

potential

prison

prisoner

security

steel

the

trapped

walking

white