After Nash and Joe arrive at a barricaded suspect scenario, with the suspect intent on shooting it out, a Chicago cop (Karen Decker) also shows up claiming the barricaded suspect is related to her case. Karen ends up killing the suspect, Alex Garza, but Garza is not the person she is seeking. Garza is Julio Serano's No.2 man and enforcer. Serano is a major drug dealer trying to flee the country. Garza was arranging for Serano's getaway with money launderer Lionel Jones when the deal went bad. Garza killed Lionel, with Garza getting killed by Karen.
Meanwhile, Joe is excited that Nick (Nash's father) is entering his race horse Mr. Woody in the horse's first stakes race. However, Mr. Woody suffers from a problem - the horse is melancholy and won't run.
From Garza's phone records, Evan Cortez locates Isiah Harper, a crystal-meth dealer. Nash, Karen, Joe and Evan trick Harper into revealing that Serano is coming by to pick-up drugs. Evan and Harvey stake out Harper's place, waiting for Serano to show. During the stake out, Harper is mysteriously killed by murderer with a silenced gun.
Meanwhile, Serano seeks out another money launderer, a Mr. Wilkes, to make arrangements for Serano to get out of the country. Nash, Joe and Karen arrive at Harper's apartment and suspect Harper was killed by Serano. Joe sees a program on Harper's television set for an animal hypnotist, and sees a solution to Mr. Woody's problem.
Nash and Karen's date at a Chinese restaurant is interrupted by a call from one of Nash's snitches. The snitch gives them a tip that Serano is at the Lumber Jack Massage Parlor. Nash and Karen go there, but Serano eludes Karen after a chase and shoot-out. Nash ends up spending the night at Karen's hotel room.
The next morning, Evan and Harvey arrest Wilkes, Serano's new money launderer. Nash and Joe squeeze Wilkes, and Wilkes tells them Serano is fleeing from a bad cop out to kill Serano. The bad cop has stolen drug money, and Serano has stolen that money from the bad cop. Wilkes unknowingly provides an alibi for Serano for Harper's murder. Nash and Joe now suspect Karen is that bad cop, and that Karen has killed Harper.
Meanwhile, in practice runs, the now hypnotized Mr. Woody runs very fast. An excited Joe wants to bet the insurance money from his burned-down bar on the now record-setting Mr. Woody.
Nash plans to set-up Karen. Nash distracts her with a bogus interview with a suspect, while Evan and Joe go to search her hotel room. Serano shows up at the hotel disguised as a waiter to kill Karen, but Serano runs into Evan and Joe instead. Karen is called to the hotel. In the ensuing shoot-out, Karen is taken hostage by Serano, forcing Nash to kill Serano.
The SIU recovers Serano's money bags containing 1.4 million in cash. Nash tricks Karen, telling her the bags only contain $500,000. Karen pretends to leave for Chicago, only to return to demand the rest of the money from Nash. Nash has set-up Karen, with the rest of the SIU waiting at his apartment to arrest Karen.
Mr. Woody runs a winning race, only to abruptly stop before the finish line. Joe has mistakenly told the hypnotist the horse was to run a mile and 1/8 instead of a mile and 1/4. But Joe doesn't lose his money, because his son J.J. bungled at putting down the bet money in time before the race was to begin.
For more, see commentary for Episode 28