T'was beauty that brought down the Russian spy ring.

A nervous Anna Chapman's phone call to her father in Moscow lit a fire under federal investigators, and sparked the arrests of her and her fellow secret agents, the Washington Post reports.

Federal officials had begun planning to round up the suspected spies in early June, and were monitoring the movements of several members of the elaborate ring, when the alarming phone call occurred.

According to the report, Chapman became suspicious after a meeting with an FBI informant, who misled her as to who he was and then asked her to perform a task that was more elaborate than her usual missions.

The informant, known as "Roman," asked that she do a face-to-face transfer of a fake passport to another agent, the Washington Post reports.

Chapman bought a cellphone and two calling cards on June 26 and contacted her dad, Vasily Kushchenko, as well as another friend in New York. They warned her not to go forward with the transfer.

Kushchenko told her to take the passport instead to the police, which Chapman did the following day. The NYPD called the FBI, who questioned the 28-year-old real estate mogul, then arrested her.

The phone call also led authorities to arrest another of the spies, Richard Murphy, who was scheduled to go to Moscow for a regular meeting with intelligence officials there. Fearing he wouldn't return as a result of the call, they picked him up. The rest were soon arrested as well.

The 10 spies have since been traded with Russia for four double agents working for the U.S. and Great Britain. An 11th spy, who was arrested in Cyprus but later released on bail, has not been found.

msheridan@nydailynews.com; or follow him at Twitter.com/NYDNSheridan