Two men and a frogman row out to the Fortuna
towing a mine. The man in charge, Nigel, orders the frogman into the water. The frogman tows the mine to the side of the casino ship while Nigel uses a lantern to signal another ship.
Later, a woman named Sylvana is playing craps. Andamo has Lucky sign off on a gambler's check and he does so, while Sylvana glances at the watch. She then argues with Joe the croupier, insisting that her bet for $1,000 paid off. Lucky comes over as another gambler confirms that he was the only one who had money on the number, but Sylvana continues making a scene. Lucky tells Andamo to pay the woman and escort her off of the ship, but she refuses to go.
A crewman on the deck notices the frogman attaching the mine to the anchor line. The frogman swims off as the crewman, Steve, sends someone in to get Lucky. When Lucky confirms that it's a mine, he has the patrons escorted to the launch. Meanwhile, Lucky calls Rovacs and has him bring a Navy demolition man. The Navy man arrives, confirms that the mine is safe, and the crew bring it aboard. They open it up and discover that it contains nothing but some wax-coated envelopes. Inside are packets of gems.
Rovacs goes with Lucky to his office and has his assistant call in the Feds. The lieutenant explains that smugglers have been bringing the gems in for months. He figures the smugglers have been using the Fortuna
as a storage location, and Lucky realizes that Sylvana was there to create a distraction. Unfortunately, they can only describe her as "beautiful." Rovacs figures that the smugglers have to come to them to get the gems back. He asks Lucky to put the gems in his safe, pointing out that the smugglers will come after him regardless once they discover that the mine is gone. Lucky reluctantly agrees and Rovacs tells the owner to contact him when the smugglers call.
Nigel is at home receiving a briefing on what happened from his assistants, Webb and Blake. Blake figures that Sylvana tipped Lucky off, but Sylvana insists that she didn't. Nigel figures that their best chance to recover the gems is to go to Lucky. He turns to Sylvana and tells her that she'll have to be creative.
Rovacs and his men are waiting on the Fortuna
when Lucky receives a call. It's Sylvana and she asks Lucky to meet her. She claims that the smugglers will kill her and Lucky agrees to come alone. Once he hangs up, Lucky tells Rovacs that the caller was his mother and walks off.
Lucky drives to the address and Sylvana says that she did her part but the frogman botched it. She explains that now the smugglers think she made a deal with Lucky and threaten to kill her if she doesn't get the gems back. Lucky doesn't believe her but Sylvana begs him to help. He suggests that she go to the police and Sylvana agrees. However, as they walk off, Webb and Blake step out and club Lucky unconscious as Sylvana smiles in satisfaction. They drag Lucky to their car and drive off.
Lucky wakes up in a steam cabinet in an exercise room as Nigel gets a massage. Nigel says that they both explain that terror is a business measure and threatens to plant a live mine on the Fortuna
if Lucky doesn't hand over the gems. Lucky warns him that there are police on the ship and they have the gems, and Nigel tells him to tell them the truth... up to a point. Once the police give him the gems to set a trap, Lucky will give Nigel the gems. Webb and Blake take Lucky out, blindfold him, and drive him back into town.
Back on the ship, Lucky calls Andamo to his office and complains about how he's been threatened. Rovacs comes in and Lucky tells him that he's been contacted and explains Nigel's plan. He figures that the smugglers will contact him the next night and asks to borrow a transmitter from the Army. Rovacs agrees and Lucky asks the lieutenant to have his men in the lab fix up a briefcase with a tear gas bomb.
The next night, Lucky loads the gems in the rigged briefcase. Rovacs assures him that they can track the transmitter up to a couple of miles away. Andamo goes with Rovacs while Lucky waits for the call. The smugglers soon make contact and give him instructions to switch taxi cabs three times to throw off any followers. Lucky finally arrives at a deserted street and a nearby car flashes its headlights. The casino owner gets into the car with Sylvana and Blake. Blake insists on opening the briefcase, setting off the tear gas. Lucky gets Sylvana out and subdues Blake, and forces the thug to tell him Nigel's name and address.
The police follow Lucky to Nigel's estate. He ushers Blake and Sylvana inside at gunpoint after placing the transmitter on the ground. Once he's inside, Lucky hands the gun over to Nigel and claims that Blake tried to steal the gems. Nigel checks the case and confirms that the gems are there. He then tells Lucky that he has no choice but to kill him.
The police pull up outside and Andamo slips into the house. Meanwhile, Webb escorts Lucky out at gunpoint. Rovacs calls out, announcing that the house is surrounded. Lucky warns Nigel that kidnapping is a federal crime. As he talks, he spots Andamo upstairs. Lucky keeps them distracted and Andamo tosses a vase. When they turn, Andamo leaps down and Lucky joins in the fight. The partners take out Webb and Blake while Sylvana runs to Nigel. He shoots at them and they duck back, and Rovacs and his men run in. Nigel shoots at them and they have no choice but to shoot him down. Lucky and Andamo walk off after picking up the transmitter.