Hush told Batman that Alfred would die - the blood he'd been infected with would kill him. Only the blood of Cassius Clay could save the victims.
Just as Hush had hoped, Batman broke into Arkham to snatch the "pure" Clayface. He explained to Cassius what was going on and asked for his help. Batman was able to spray him with something so he would revert to human form. Police and SWAT attacked as Batman and Cassius exited Arkham. In the melee, Hush got three samples, but was smashed by Clayface. The new Clayface, working with Hush, confronted Cassius. After the battle, the new Clayface ended up with the sample. He gave it to Batman and asked that he save his family from Hush.
The detectives were given a warrant to arrest Alfred.
Bruce showed the detectives that the dead man (the new Clayface died) had near identical prints to Alfred. The case was dropped.