10. Doubt
L and Light play tennis and try to size up each other. Light tries to find a way to get onto the investigation team without rising the suspicion that he might be Kira. But L beats him in this regard and plainly tells him that he suspects him, but wants him on the team nonetheless. If he isn't Kira, he would be a great help on the investigation. If he is Kira, he might trip up and reveal himself.
Light's father has a conversation with the chief of the police, where the chief wants to know the identity of L and Light's father refuses to tell him.
Light's father gets an heart attack but it turns out to be only fatigue.
At the end a television studio gets some tapes which are asked to be played on the air.
This episode covers the manga chapters 20-22. Essentially the same things happen except that the manga elaborates more.
In the movies, the tennis match was replaced by a chess game where both size up each other. The heart attack of the father probably inspired the ending of the second movie. The way that Light gets on the team is also much different. Essentially the whole ending of the first movie is an elaborate plan by Light to defuse the suspicion from him by letting his girlfriend be killed by Kira. He also uses it as reasoning to get on the team to "find" the killer of his girlfriend. L reveals to Light non-verbally that he suspects him being Kira by eating a special brand of chips in front of him. The same kind of chips Light used to hide the Death Note while writing down names while he was being survaillanced.
Also in the movies Light's father visits the chief of police and also a television studio gets tapes to play.