The 1936 film "The Black Coin" is about Secret Service operatives chasing smugglers and a whole group of people chasing the "Black Coins" which point to a treasure. This serial film had 15 chapters, each about 15 minutes long, and was released in September of 1936. The title coins are Arabic, overstruck with Christian symbols during the Crusades. Many years later twelve of these were marked to show the location of a treasure. Over time, the silver content has caused the coins to turn black. The treasure was saved from a pirate ship by the crew of the "Santa Clara", a Spanish ship off the coast of California, who buried the treasure and marked the location on the twelve coins. The heroes are Secret Service agents, Dorothy Dale and Walter Prescott who start off tracking smugglers using the Caswell Shipping and Salvage Company. The company's president Frank Caswell may be involved with the smugglers. Terry Navarro is an agent of Mr. Caswell who buys one of the "Black Coins" from a street salesman. The villians are members of a smuggling ring, headed by Henry Jensen, whose agent James Hackett works for Caswell's company as a business manager. Captain "Shark" Malone is a sea captain working with Hackett. The character Dorothy Dale may be based on Dorothy Gale, a heroine of a series of novels written beginning in 1898 and continuing up to and past when the film was made. This film has plenty of action and story is too long to tell in detail with continual fights, captures, and rescues of the players. The "Black Coins" appear several times and are portrayed by dollar-size prop coins with the face of a man wearing a turban on one side. Sometimes the word "Santa Clara" appears on a coin.

The film opens with a Foreword:

The coins in the film are fictional but the Crusaders actually did copy Islamic coins for use in the Middle East but did not put Christian symbols on them.

The story starts in Tangier Morocco with a scene of some Arabs riding.

Terry Navarro has bought a coin from a street person and asks a dealer what it is.

The title "Black Coins" appears almost immediately.

The obverse shows a man wearing a turban. The action continues with a cliff-hanger where Terry Navarro is on an airplane which explodes.

Terry survives, of course. A group of smugglers discuss operations.

Smugglers: Henry Jensen, James Hackett, Captain Malone, Vic Moran The action moves to a sheep ranch "out west" which the smugglers are using.

Some western riders are heading somewhere. The "Black Coins" appear again.

Two "Black Coins" appear, this time with the word "Santa Clara" written on them. At the end of Chapter 3 Dorothy Dale drives a car off of a drawbridge being raised.

Dorothy escapes the accident when the drawbridge operator spots her car coming and lowers the bridge. The "Monsters of the Deep" are various modern day pirates.

Dorothy and Terry with a sheriff encounter a local crook. Some of the smugglers are also after the coins.

A hand reaches out for Don Pedro Navarro, Terry's father, who owns some of the coins.

A coin holder with three of the coins. Crooks capture Walter and Dorothy.

Walter has a knife and manages to untie himself and Dorothy. On their boat, Captain Malone takes out his six coins.

The captain and a crew member fight over the coins, during the fight a can of gasoline explodes and destroys the ship.

The smugglers are all arrested putting an end to their activities. Mr. Caswell is cleared of being involved with the smugglers. Since half of the twelve treasure coins went down on the ship, the others are useless as guides to the treasure and Mr. Caswell hands his coins to the two Secret Service operatives and the people who assisted them.

Ralph Graves as Walter Prescott
Ruth Mix as Dorothy Dale
Dave O'Brien as Terry Navarro
Constance Bergen as Virginia Caswell
Mathew Betz as Henry Jensen
Robert Frazer as James Hackett
Snub Pollard as Vic Moran
Robert Walker as Captain "Shark" Malone
Director: Albert Herman
Writers: George M. Merrick, Dallas M. Fitzgerald, Eddy Granemann, Bob Lively, Albert Herman