HST/WFC3¹ composite image (F160W, F814W, F475X) of J1721+8842. The six lensed point images of the background quasar are labelled with letters. The red lensed arc, previously believed to be the host galaxy of a second source quasar, is highlighted in white. This arc is actually an additional deflector at an intermediate redshift, which is itself lensed by the central foreground galaxy in the image. The dotted red square indicates the footprint of the JWST/NIRSpec observation that enabled the measurement of the arc’s redshift.