Modest Mouse fans have been getting some strange mail from the band this month to promote a new single.

Pictures of the package started showing up on Twitter and Reddit on Tuesday, and inside is a puzzle that reveals the title of a new single called “Poison the Well” that will be out on March 29th. The puzzle also states that a seven-inch single with that song and an unreleased B-side will be out for Record Store Day on April 13th.

Modest Mouse’s last album was 2015’s Strangers to Ourselves. They’re expected to release a full new album before hitting the road with The Black Keys in the fall.