Last year was a vintage year for mobile group II introns. In 1995 we moved from phenomenology to mechanistic insight, from enigmatic observations to a coherent appreciation of process. The finding that nucleated our understanding of the group II intron mobility event was the appearance of an extraordinary double-strand break in the target DNA: a break that provides an initiation site for reverse transcriptase, which mediates group II intron mobility; a break in which the excised intron RNA is covalently attached to one of the DNA ends; a break that is made by the protein and RNA products of the intron itself, with the RNA believed to be the catalyst responsible for one of the DNA strand cleavages. In this minireview, we piece together the puzzle by describing the formation of this remarkable double-strand break, its role in group II intron mobility, and the evolutionary implications of the process.