  We study asymptotic behavior, for large time $n$, of the transition
probability of a two-dimensional random walk killed when entering into a
non-empty finite subset $A$. We show that it behaves like $4 \tilde u_A(x)
\tilde u_{-A}(-y) (\lg n)^{-2} p^n(y- x)$ for large $n$, uniformly in the
parabolic regime $|x|\vee |y| =O(\sqrt n)$, where $p^n(y-x)$ is the transition
kernel of the random walk (without killing) and $\tilde u_A$ is the unique
harmonic function in the 'exterior of $A$' satisfying the boundary condition
$\tilde u_A(x) \sim \lg |x|$ at infinity.
