what does "nutshell"here mean?
“Huh.” Vinnie’s gaze shifted from the trench to Eli’s. “Is that right?”
“Gran didn’t have a reason, not one she could articulate, but she was adamant about it. She doesn’t clearly remember the fall, but I wonder if there’s an instinct, some buried memory, something that had her insist-ing on changing the security.”
“You find a hole in the basement and now you think Miss Hester’s fall wasn’t an accident.”
“Yeah, nutshell. Abra was assaulted last night. He had to cut the power to get in. He wasn’t expecting her. He knew I wasn’t here. Maybe he’s working with Duncan. Duncan knew I was in Boston. You said he showed you receipts, gave you timelines. He could’ve given the per-son who broke in the all-clear. I’m in Boston, get in, get digging.”