We report the recovery of a spectroscopic event in \eta Carinae in 1997/98 after a prediction by Damineli ( 1996 ) .
A true periodicity with P = 2020 \pm 5 days ( 0.2 % uncertainty ) is obtained .
The line intensities and the radial-velocity curve display a phase-locked behavior implying that the energy and dynamics of the event repeat from cycle to cycle .
This rules out S Doradus oscillation or multiple shell ejection by an unstable star as the explanation of the spectroscopic events .
A colliding-wind binary scenario is supported by our spectroscopic data and by X-ray observations .
Although deviations from a simple case exist around periastron , intensive monitoring during the next event ( mid 2003 ) will be crucial to the understanding of the system .