Orlando Bloom and his guilty-by-association co-star Keira Knightley have mercifully walked the plank. Finally, the fourth installment of the Pirates of the Caribbean franchise has found its way toward coherence.

As the director of sturdy movies such as Chicago and Memoirs of a Geisha, Rob Marshall is better suited to carry off the adventure franchise's obligatory chase-action set pieces and recurring sword fights than former helmer Gore Verbinski. The first 15 minutes of the movie are set in 18th century London and have a playful feeling more akin to an Indiana Jones picture than the forced romance and creepy horror of Verbinski's overly busy kitchen-sink efforts.

We first see Capt. Jack Sparrow (Johnny Depp) from the back. He's disguised as a British judge busy hearing a case against a man believed by the rest of the court to be Jack. Jack's planned escape from the courthouse lands him in the unexpected company of King George II (delightfully played by the ever-reliable Richard Griffiths).

The scenery on display is especially enjoyable. Jack is rumored to have in his possession a map that points to the fabled Fountain of Youth. King George informs Jack there is a Jack Sparrow imposter roaming around London searching for men to run crew for an unknown expedition. Enter Jack's longtime rival Barbossa (Geoffrey Rush). Since the last movie, Barbossa has lost a leg and turned over a new leaf to work for king and country. Barbossa's peg-leg charge is to find the Fountain of Youth before the Spanish can beat the Brits, or any pirates, to the punch.

Penélope Cruz plays Jack's former love interest Angelica. In the years since Jack rescued her, Angelica has discovered Blackbeard (Ian McShane) to be her biological father—maybe. Cut to Angelica kidnapping Jack onto Blackbeard's ship so her old flame can lead them to the fountain of eternal life for the sake of her dying pirate papa.

The rollicking tides the competing ships must cross are made "strange" by the presence of long-tailed mermaid sirens who are every bit as beautiful as they are treacherous. Their perfect teeth can transform into fangs at a moment's notice. Mermaids have never played such a significant role in an adventure film; their exotic nature is contrasted with an element of horror that captures and toys with the imagination.

Pirates of the Caribbean: On Stranger Tides is Depp's movie. He has embraced Jack Sparrow as a kind of alter ego and built on his own legacy. Depp is clearly having fun. And so are we.