By numerical simulations, the dynamical behaviour of the electrons in one-dimensional double layers is studied. The simulation results show that at least one third of the electrons emitted at the low-potential boundary of the simulation system are reflected back before passing through the double layers. Such reflexion is due to (i) quasi-linear or nonlinear scattering by plasma oscillations and (ii) ambipolar potentials observed around the potential front of the localized double layer. The whole temporal evolution of the localized double layers are also presented. In particular, we attempt to explain the steepening and collapsing of the localized double layers in terms of the formula for the double-layer thickness.