Death Note!

[Dr. Boogie]

They watch the Yotsuba guys talk about who they'll kill next, and Light's dad wants to arrest them on that, but L wants to let them kill the next few people so they'll have definitive proof and be that much closer to catching Kira. Light calls one of the board members, pretending to be L, and blackmails him into delaying the killings for a month.

At the end of the episode, the investigative teams splits up; Light's dad, Matsuda, and that other guy try to figure out the best way to arrest all the board members, and L devises a plan to use Misa to help root out Kira. Light joins him because they're handcuffed together.