We present theoretical calculations of temporal variations in the nonthermal redshifted Ly-alpha emission due to time-invariant proton beams injected into a stellar atmosphere during the impulsive phase of a flare. The computations are performed for a power law spectrum of nonthermal proton energies injected into a model stellar atmosphere consisting of pure hydrogen in local thermodynamic equilibrium; beam-induced variations in temperature and particle densities at all depths and for all times are calculated with the Saha equation. We characterized the injected model proton beams with the total energy flux F and the power law index d, and computed time-dependent nonthermal redshifted Ly-alpha emission profiles for five different values of F and three different values of d. Based upon trends evident in the resulting emission, proton beam properties can be deduced from sufficiently high quality observations of the nonthermal redshifted Ly-alpha profile. The beam penetration depth initially decreases with time, but in most cases it increases again after reaching some minimum value. This behavior is due to changes in the ionization and temperature of the atmosphere. The Ly-alpha intensity also initially decreases with time, but in most cases it reaches a relative minimum, increases again to a secondary relative maximum, and then slowly but steadily decreases thereafter. Observable properties of this time-dependent emission can be used to deduce both d and F.