Bestowed with superpowers when a lab experiment goes unexpectedly awry, an average beagle becomes the savior of Capitol City as everyone's favorite canine do-gooder embarks on his first-ever live-action adventure. The maniacal Dr. Simon Barsinister (Peter Dinklage) was on the verge of a revolutionary discovery when a sudden mishap gave birth to Underdog (voice of Jason Lee). Not only can this remarkable mutt now leap tall buildings in a single bound, be he can let his "best friend" know precisely what's on his mind in no uncertain terms as well. When Dr. Barsinister and his overgrown crony Cad (Patrick Warburton) threaten to destroy Capitol City, Underdog must leap into action in order to protect the frightened citizens and ensure that no harm comes to pretty Polly Purebread (voice of Amy Adams).