We show that a plane continuum
X
X
is indecomposable iff
X
X
has a sequence
(
U
n
)
n
=
1
∞
(U_n)_{n=1}^\infty
of not necessarily distinct complementary domains satisfying the double-pass condition: for any sequence
(
A
n
)
n
=
1
∞
(A_n)_{n=1}^\infty
of open arcs, with
A
n
⊂
U
n
A_n \subset U_n
and
A
n
¯
∖
A
n
⊂
∂
U
n
\overline {A_n}\setminus A_n \subset \partial U_n
, there is a sequence of shadows
(
S
n
)
n
=
1
∞
(S_n)_{n=1}^\infty
, where each
S
n
S_n
is a shadow of
A
n
A_n
, such that
lim
S
n
=
X
\lim S_n=X
. Such an open arc divides
U
n
U_n
into disjoint subdomains
V
n
,
1
V_{n,1}
and
V
n
,
2
V_{n,2}
, and a shadow (of
A
n
A_n
) is one of the sets
∂
V
n
,
i
∩
∂
U
\partial V_{n,i}\cap \partial U
.