  The structure and mobility of dislocations in the layered semiconductor InSe
is studied within a multiscale approach based on generalized Peierls--Nabarro
model with material-specific parametrization derived from first principles. The
plasticity of InSe turns out to be attributed to peculiarities of the
generalized stacking fault relief for the interlayer dislocation slips such as
existence of the stacking fault with a very low energy and low energy barriers.
Our results give a consistent microscopic explanation of recently observed
[Science {\bf 369}, 542 (2020)] exceptional plasticity of InSe.
