Simulations of plasmon-enhanced high-order-harmonic generation are performed for a H-2(+) molecular cation near the metallic nanostructures. We employ the numerical solution of the time-dependent Schrodinger equation in reduced coordinates. We assume that the main axis of H-2(+) is aligned perfectly with the polarization direction of the plasmon-enhanced field. We perform systematic calculations on plasmon-enhanced harmonic generation based on an infinite-mass approximation, i.e., pausing nuclear vibrations. Our simulations show that molecular high-order-harmonic generation from plasmon-enhanced laser fields is possible. We observe the dispersion of a plateau of harmonics when the laser field is plasmon enhanced. We find that the maximum kinetic energy of the returning electron follows 4U(p). We also find that when nuclear vibrations are enabled, the efficiency of the harmonics is greatly enhanced relative to that of static nuclei. However, the maximum kinetic energy 4U(p) is largely maintained.