Difference images for part of the MHO 2235 flow including the position of the Class I sources Ser-emb-17 and Ser-emb-11 E and W (red circles) and two YSO candidates from Harvey et al. (2006; magenta circles), cf. Fig. 4. The image shifts are in the direction: ep2-ep1 (upper left), ep3-ep2 (upper right), ep4-ep3 (lower left), and ep4-ep1 (lower right), bright regions showing positive flux. The brightening near knot A1 appeared in the 2011 image and had disappeared again in the 2013 image.