New York has dropped five straight games to sink into last place in the Metropolitan Division.
Helm scored the only goal registered in each of the first and second periods. His second goal came shorthanded with 3:11 to go in the middle stanza.
Detroit broke things open with three goals in the final period. Alfredsson scored just 12 seconds into the period, Gustav Nyquist tallied six minutes later and Alfredsson completed the scoring with 3:47 to go.
All five goals came against Kevin Poulin, who faced 30 shots.