英语听力：自然百科 探索世界奥秘之FBI(揭密联邦调查局)Unit7（在线收听）

Despite the risk, Spence allows the FBI to rig a video camera in the dashboard of his truck. Here, the hidden camera records one of the suspects describing how he is going to make a bomb. But getting a conviction in this case will require more than just words caught on tape. Garrity says the FBI has to prove that the suspects intend to kill. With the conspiracy, there has to be some overt acts committed, there has to be a point, when they go beyond speaking, and go towards acting. Finally, the bureau gets the break it needs, when it learns that the Klansmen are going to a field to test their homemade bombs. The Feds come up with a simple and remarkably effective plan. They give Spence an ordinary home video camera and tell him to record his friends as they prepare and detonate the explosives. In case the Klansmen question why Spence has a camera, the FBI gives him a cover story.

To watch video tape goes was kind of amusing really. I told them that I was trying the thing out----see if it won't abide. So that was a good time to test it.

The actions caught on video tape are enough to convince the agents that the Klansmen are about to follow through with their terrifying scheme.

I have gotten certain of homemade explosives around. And I have got to remind you what they set off over two min.

But even though the tape is startling, the FBI still needs more evidence. Four weeks into the operation, they finally get it. The Klansmen go to the refinery to finalize their plans. They talk about the bombing in explicit detail. This is the video tape, it seals the Klansmen's fate.

Then comes the most chilling evidence of all. As the conspirators drive by a house across the street from the refinery, a tragic consequence of their plan is revealed.

The FBI now has all it needs to make the arrest, they instructs Spence to drive the Klansmen to a gas station, there, the Feds make their move.

rig: to furnish with special gear

overt: plain, clear, visible; done or shown openly

follow through: continue in an activity until its conclusion, complete