  We report the discovery of a new Kepler first-overtone RR Lyrae pulsator, KIC
2831097. The pulsation shows large, 0.1 d amplitude, systematic phase
variations that can be interpreted as light travel-time effect caused by
orbital motion in a binary system, superimposed on a linear pulsation-period
decrease. The assumed eccentric (e=0.47) orbit with the period of approximately
2 yr is the shortest among the non-eclipsing RR Lyrae binary candidates. The
binary model gives a lowest estimate for the mass of the companion of 8.4
M_Sun, that places it among black hole candidates. Beside the first-overtone
pulsation, numerous additional non-radial pulsation frequencies were also
identified. We detected an ~47-d Blazhko-like irregular light-curve modulation.
