BALTIMORE — A man accused of kidnapping his 7-year-old daughter during a supervised visit in Boston and whisking her through New York was arrested Saturday in Baltimore and the girl was found safe, authorities said.

A “concerned citizen” tipped off authorities that the man known as Clark Rockefeller was living in a Baltimore apartment and had a 26-foot catamaran docked at a nearby marina, Boston Police Commissioner Ed Davis said.

Mr. Rockefeller will be arraigned Monday to begin extradition proceedings. He is charged with felony custodial kidnapping, assault and battery, and assault and battery with a dangerous weapon, Mr. Davis said.

Investigators invented a ruse to get Mr. Rockefeller out of the apartment and away from the child. They called the suspect and told him that his boat was taking on water.

He was arrested when he left the apartment, Mr. Davis said. The girl, Reigh Boss, was found apparently unharmed inside.

“Her first words were she was very happy to see very nice people … she was ecstatic,” said Noreen Gleason, FBI’s assistant special agent in charge of the Boston division.

The girl lives with her mother, Sandra Boss, who works in London as a partner in a global management consulting firm. The mother collapsed after hearing that her daughter was found alive and was en route to Baltimore. “She fainted, in a way,” Boston Police Deputy Superintendent Tom Lee said.

The arrest ended a suspenseful week that began in Boston’s Back Bay neighborhood when police said Mr. Rockefeller attacked and fled from a social worker during a supervised visit with his daughter.

In what police believe was an elaborate plan, Mr. Rockefeller is accused of arranging for two drivers to take them to New York City. He was most recently spotted last Sunday at Grand Central Terminal in New York City.

Police first believed Mr. Rockefeller was trying to flee to Bermuda or Peru on a yacht docked on Long Island. But later they found he might have planted false clues to throw investigators off his trail.

The father and daughter did not appear to have sailed to Baltimore, because the catamaran has been docked there all along.

Mr. Davis said the investigation was ongoing and authorities were still trying to determine Mr. Rockefeller’s real identity and if anyone else was involved in the abduction.

Mr. Rockefeller used at least four known aliases, and there is no indication the fugitive is related to the famous family descended from Standard Oil billionaire John D. Rockefeller Sr., family members said.