Lightnin' wins (1926)

Lightnin' the dog and his master, Tom Harding are on to a group of smugglers who operate down at the harbor. Tom nearly bags them, but he's overwhelmed and they take flight. His girlfriend bluffs her way into the gang's hideout, but is discovered and held back. Tom is again overpowered by the crooks and thrown in a secret dungeon, but he fights his way out.