We present the results of a recent reverberation-mapping campaign undertaken to improve measurements of the radius of the broad line region and the central black hole mass of the quasar PG 2130+099 . Cross correlation of the 5100 Å continuum and H \beta emission-line light curves yields a time lag of 22.9 ^ { +4.4 } _ { -4.3 } days , corresponding to a central black hole mass M _ { BH } = ( 3.8 \pm 1.5 ) \times 10 ^ { 7 } M _ { \odot } . This value supports the notion that previous measurements yielded an incorrect lag . We re-analyzed previous datasets to investigate the possible sources of the discrepancy and conclude that previous measurement errors were apparently caused by a combination of undersampling of the light curves and long-term secular changes in the H \beta emission-line equivalent width . With our new measurements , PG 2130+099 is no longer an outlier in either the R _ { BLR } – L or the M _ { BH } – \sigma _ { * } relationships .