For more than a year, Special Counsel Robert Mueller’s office has questioned witnesses broadly about their interactions with well-connected Russians. But three sources familiar with Mueller’s probe told The Daily Beast that his team is now zeroing in on Trumpworld figures who may have attempted to shape the administration’s foreign policy by offering to ease U.S. sanctions on Russia.

The Special Counsel’s Office is preparing court filings that are expected to detail Trump associates’ conversations about sanctions relief—and spell out how those offers and counter-proposals were characterized to top figures on the campaign and in the administration, those same sources said.

The new details would not only bookend a multi-year investigation by federal prosecutors into whether and how Trump associates seriously considered requests by Moscow to ease the financial measures. The new court filings could also answer a central question of the so-called “Russia investigation”: What specific policy changes, if any, did the Kremlin hope to get in return from its political machinations?