Volcanalis " is the 18th episode and of the supernatural drama television series '' Grimm '' of season 2 and the 40th overall , which premiered on April 26 , 2013 , on NBC . The episode was originally scheduled to air on April 19 , but it was preempted for coverage related to the Boston Marathon bombing . The episode was written by series creators Jim Kouf and David Greenwalt , and was directed by David Grossman
Boston Marathon bombing
Boston Marathon bombing
Volcanalis