Tremble

 Tremble (震える, Furueru) is the 9th chapter of Volume eight and 70th chapter overall.

Plot
In a flashback sequence, after Light figures out that Jack Neylon is the current Death Note owner, Sidoh sees his picture and finds him quickly after scanning the human world from the shinigami realm. He goes to Mello’s location where Jack is and throws the notebook so that it touches Jack, making him see Sidoh. He explains to Jack that he is a shinigami, and if everyone else touches the notebook, then they will all see him.

After Sidoh becomes visible to everybody, Mello and his men grill him with questions. They figure out that the “If you don’t use the Death Note after 13 days, you will die” rule is fake. Mello wonders if Kira knew about this fake rule, and if so, if he used it to his advantage. Mello then asks him about other Death Note owners, but Sidoh answers that he can’t talk about them. Mello then forces Jack to trade half of his lifespan for the shinigami eyes. He also tells Sidoh that once they get the Death Note from Kira, they will give it to him if he promises to help them by standing guard outside and pulling intruders toward the cameras.

Back in the present, this is exactly what he has done to the special task force. Light quickly realizes that it’s another shinigami. Aizawa suggest that they contact the SPK for help. However, Light doesn’t want Near involved, fearing that he’ll become suspicious as to how he found Mello’s hideout.

Light confronts Ryuk about the shinigami, and Ryuk tells him that he found Light’s notebook in the shinigami realm so the owner was the original shinigami who dropped it. Light asks Ryuk if shinigami are allowed to talk about other Death Note owners, and he answers no. Still, he fears that Misa and most importantly, her shinigami eyes will be killed by Jack Neylon once he figures out with his shinigami eyes that Misa is a Death Note owner. He makes Misa quit her career and promises to marry her.

Mello’s gang has evacuated from their hideout. They call several high-ranking officials, including the president of the U.S., demanding to know who was it that instigated the ambush, but they have all committed suicide. Mello wonders who could have figured out where they were hiding.

Conception
Ohba said the chapter's title "Tremble" relates to two different instances where Sidoh trembles. The first one is when he feels frightened by Mello, and then the second one is when he feels frightened by the prospect of Shinigami world punishments.