Position–velocity cut of HDO(3_3,1–4_2,2) (colour scale, magenta contours) along (left panels) and perpendicular (right panels) to the equatorial plane (PA = 112°; see Fig. 1) overlaid with the CH₃CHO(18_0,18–17_0,17)-E (upper panels) and CH₃CHO(18_0,18–17_0,17)-A (lower panels), drawn as white contours. The first contours and steps correspond to 3σ (3.1 K km s⁻¹). Dashed lines mark the position of the HH 212 mm protostar and the cloud V_LSR (+1.7 km s⁻¹; Lee et al. 2014). The error bars are drawn in the bottom right corners.