This is Ruth Duck’s take on the Nunc dimittis (Luke 2:29-35), with further inspiration, apparently, from the “Narnia Chronicles”. Here it is set to to DICKSON by Norah Duncan IV.
It is listed for the “Presentation of the Lord”, but could conceivably be a recessional for a harassed priest.
You can get the text and an idea of the sheet music from the preview at Hymnary, but it isn’t available at GIA as a single sheet, although they do have an alternative setting, CONDITOR ALME SIDERUM, on sale for the chant aficionados.
In the absence of any clues on the internet as to how this should go, the music suggested a gentle cha cha cha.