Top panels: dynamic spectra of three absorption lines of MWC 314 in the heliocentric velocity scale. Blue colours correspond to normalised stellar continuum flux levels. Bottom panels: corresponding normalised line profiles shifted upwards with orbital phase (spectrum numbers are labelled in the left-hand panel). The (S-shaped) Doppler shifts of the lines is due to the orbital motion of the primary star. We observe significant enhancements in the absorption line depth at orbital phases with large Doppler blue-shift of φ = 0.65–0.85.