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We present spectroscopy and time-series photometry of the dwarf nova QZ Ser.The spectrum shows a rich absorption line spectrum of type K4 +- 2. K-typesecondary stars are generally seen in dwarf novae with orbital periods P-orbaround 6 h, but in QZ Ser the absorption radial velocities show an obviousmodulation (semi-amplitude 207(5) km/s) at P-orb = 119.752(2) min, much shorterthan typical for such a relatively warm and prominent secondary spectrum. TheH-alpha emission-line velocity is modulated at the same period and roughlyopposite phase. Time-series photometry shows flickering superposed on amodulation with two humps per orbit, consistent with ellipsoidal variation ofthe secondary's light. QZ Ser is a second example of a relatively short-perioddwarf nova with a surprisingly warm secondary. Model calculations suggest thatthe secondary is strongly enhanced in helium, and had already undergonesignificant nuclear evolution when mass transfer began. Several sodiumabsorption features in the secondary spectrum are unusually strong, which mayindicate that the present-day surface was the site of CNO-cycle hydrogenburning in the past.Comment: 11 pages, 3 postscript figures, 1 jpeg greyscale figure. Accepted for  publication in PAS

QZ Serpentis: A Dwarf Nova with a 2 Hour Orbital Period and an Anomalously Hot, Bright Secondary Star