In the fourth episode of the campaign, "Apprehend the Underground Fight Organizer", use the following combinations:
Explore + Police Work = Captain Morris, Help, Mate, Police Station
Explore + Mate = Danny
Help + Help = Deal
Danny + Money = Debtor Danny
Explore + Police Station = Coffee, Phone
Coffee + Debtor Danny = Detective Nicolas
Explore + Detective Nicolas = Detective Nicolas, Informant Contracts
Informant Contracts + Phone = 15:30, Pizzeria
15:30 + Pizzeria = Informant Chuck, Pizzeria
Informant Chuck + Deal = Informant Chuck, Ronald's House
Explore + Ronald's House = Arrest, Bribe, Ronald
Bribe + Ronald = Closed Case, Money
The achievement should then unlock.