  We consider a pair of parallel straight quantum waveguides coupled laterally
through a window of a width $ \ell $ in the common boundary. We show that such
a system has at least one bound state for any $ \ell>0 $. We find the
corresponding eigenvalues and eigenfunctions numerically using the
mode--matching method, and discuss their behavior in several situations. We
also discuss the scattering problem in this setup, in particular, the turbulent
behavior of the probability flow associated with resonances. The level and
phase--shift spacing statistics shows that in distinction to closed
pseudo--integrable billiards, the present system is essentially non--chaotic.
Finally, we illustrate time evolution of wave packets in the present model.
