  We investigate the destiny of a gray soliton in a repulsive one-dimensional
Bose-Einstein condensate undergoing a sudden quench of the non-linearity
parameter. The outcome of the quench is found to depend dramatically on the
ratio $\eta$ of the final and initial values of the speed of sound. For integer
$\eta$ the soliton splits into exactly $2\eta-1$ solitons. For non-integer
$\eta$ the soliton decays into multiple solitons and Bogoliubov modes. The case
of integer $\eta$ is analyzed in detail. The parameters of solitons in the
out-state are found explicitly. Our approach exploits the inverse scattering
method and can be easily used for the similar quenches in any classical
integrable system.
