At the beginning of the third season of “Succession,” Kendall Roy, played by Emmy-winner Jeremy Strong, was on a high: and for once, the reason was virtuous, not chemical. His attempt to overthrow his father, Logan (Brian Cox), from Waystar Royco — the family business that happens to be a multinational conglomerate — appeared to be going well. But for Kendall, peaks quickly tend to become valleys. As Strong puts it during a conversation with “Succession” executive producer Adam McKay moderated by Variety, in those early episodes, “I thought a lot about Uncle Albert from ‘Mary Poppins’ — the laughing, floating guy, trying to keep up this positivity that is really a desperate dance over an abyss.”

By “Too Much Birthday” — the season’s seventh episode, set at Kendall’s 40th birthday party — Strong says he knew it would “have the genome of the whole season in this one episode in terms of Kendall’s arc,” with the character starting out exhilarated, only to be brought to “the nadir of his life.”

After the episode’s table read, with Strong “feeling like there might be more there to mine,” “Succession” creator Jesse Armstrong added something that the actor says is its key: Kendall’s search for his kids’ present. His ex-wife, Rava (Natalie Gold), has told him their children made him a gift, one with rabbit wrapping paper. And once Kendall realizes that despite all the care he’s put into the planning, his celebration “just feels like an asshole’s birthday party,” he begins to spin out — and starts a desperate search for the present.

The scene was revelatory for Strong. “There’s a line in the text where he says, ‘I wish I was…,’ and then there’s an ellipses: ‘I wish I was home,’ And I didn’t know this working on it, but when I got to the day — well, it’s hard to talk about.” Performing it, Strong says, made him realize that Kendall is suicidal, an idea that would continue to play out in the season’s final two episodes: “I think he just wants it all to be over,” Strong says.

Strong compares Kendall’s search for the present to the “Rosebud” mystery in “Citizen Kane” — he’s futilely looking for an untainted memento that will make him whole. “Like, whatever happiness might have existed was in his past, and he’s trying to recover it that night,” Strong says. “And he can’t.” Strong wanted the assortment of extravagant gifts — “the detritus of it” — to be huge, and sent the episode’s director, Lorene Scafaria, “sketches of what I hoped the gift pile might be like.” He didn’t want to act as if he were looking; he wanted to be looking.

“And we did hide it in there,” Strong says. “And I couldn’t find it.”

To read the entire conversation between Strong and McKay about “Too Much Birthday,” which was Strong’s Emmy submission, click here.