  The variability of HD 240121 = BD+59 2602 was first suspected by S\"arg &
Wramdemark (1970) and later confirmed by Gr\"obel (1992a,b). Because of the
observed anti-phase variations of the B and V light curves, the latter author
tentatively suggested an ACV type. Apart from its inclusion in the catalog of
New Suspected Variables (NSV 25977), no further investigations of the star have
been published. HD 240121 was included into our target list of ACV candidates
and investigated in order to determine the reason for the observed brightness
variations. All available information on HD 240121 were collected via an
exhaustive data mining procedure. Data from Gr\"obel (1992a,b) were re-analysed
and photometric observations from the NSVS and Hipparcos archives were procured
and investigated. Line-of-sight reddening and stellar parameters were
calculated from archival photometric data. HD 240121 is a young, late B-type
CP2 star of the silicon subgroup. The observed period, amplitude of light
variations and variability pattern (anti-phase variations) are typical of ACV
variables. The occurrence of anti-phase variations of the B and V light curves
is rarely observed and points to the existence of a null wavelength in the
visual spectrum. We therefore strongly encourage further multi-colour
photometric observations of this star.
