A reaction can be thought of as molecular dancers performing moves. A choreographer is needed to organise the performance into the ballet that is a reaction mechanism. Here I explore another facet of the Michael addition of a nucleophile to a conjugated carbonyl compound. The performers this time are p-toluene thiol playing the role of nucleophile, adding to but-2-enal (green) acting as the electrophile and with either water or ammonia serving the role of a catalytic base to help things along.†