
Alissa G. answered 04/16/19
Expert Editor/Proofreader, Grammar Geek, Word Nerd
Hi there! In this sentence, "trick" is definitely a verb. You might be confused because "must" is also a verb. A hint for future knowledge - "trick" would only be a noun if it were preceeded by "a" or "the", as in:
"I must show him a trick."
"Did you show him the trick?"
I hope this helps!
Warmly,
Alissa G.