In the "Sons of Anarchy" season 3 finale, the club's legal troubles with the ATF are resolved when Jax makes a deal with Agent Stahl. Tara and Gemma both find letters that reveal important secrets about Jax's plans for the club and about how Jax's father died.
Jimmy O negotiates his escape to South America through the Russian mafia. The only way that Jax can get Jimmy back to turn him over to Agent Stahl is to pay the Russians $2 million. To come up with the money, Jax gets $250,000 from Stahl and uses it to pad counterfeit bills.
The club meets with the Russians and exchanges the cash for Jimmy, thinking they plan to him as part of their deal with the IRA. Stahl waits down the road to apprehend Jimmy, but the club switches him to Tara's car beforehand.
When Stahl realizes Jimmy is not in the van, she confronts Jax, who demands the documents about their deal to reduce the club's weapon charges. Once he has them, they go to meet Tara and Clay to recover Jimmy. Stahl reveals that Jax has betrayed the club, and Clay vows revenge as they are all arrested.
Unser flags down Stahl's car for the club, telling her she will be attacked further up the road to recover Jimmy O. Opie and Chibs get out of Unser's cruiser and kill Jimmy O and Agent Stahl.
In the ATF van, Clay and Jax smile at each other, revealing that the club knew about Jax's deal with Stahl all along.
Gemma finds a letter telling her about the plan to trick Stahl and why she couldn't know about it, and Tara finds a letter from Jax's father that says that Clay and Gemma are plotting to kill him.