  The nature of shock waves in non-fundamental mode RR Lyrae stars remains a
mystery because of limited spectroscopic observations. We apply a pattern
recognition algorithm on spectroscopic data from SDSS and LAMOST and report the
first evidence of hydrogen emission in first-overtone and multi-mode RR Lyrae
stars showing the "first apparition", which is the most prominent observational
characteristic of shock in RR Lyrae variables. We find ten RRc stars in SDSS,
ten RRc stars in LAMOST, and three RRd stars in LAMOST that show blueshifted
Balmer emissions. The emission features possibly indicate the existence of
shock waves. We calculate the radial velocities of the emission lines, which
are related to the physical conditions occurring in the radiative zone of shock
waves. Using photometric observations from ZTF, we present a detailed light
curve analysis for the frequency components in one of our RRd stars with
hydrogen emission, RRdl3, for possible modulations. With the enormous volume of
upcoming spectral observations of variable stars, our study raises the
possibility of connecting the unexplained Blazhko effect to shock waves in
non-fundamental mode RR Lyrae stars.
