The bored pair sparked speculation they were on a secret task by holding private chats, followed by lots of giggling.
But their apparent plotting didn't go down well with the other housemates.
Drying their clothes in the mangle in the garden, Joe told Jack: "I think there's a task... Dexter went up stairs, looked at Hazel, then two or three minutes later, Hazel went up stairs, then they came down and were both laughing."
Sophie relayed the pair's conversation to Dexter and Hazel, who were in the kitchen eating.
She told them: "Joe's a bit pissed off you know, because yous two are laughing, he likes to know what's going on, that's why he walked out."
But Dexter insisted: "People are so sensitive, oh God, we were just having a laugh."
"There's nothing else to do in here," added Hazel.
Back out in the garden, and Jack suggested: "Maybe Dexter's chosen Hazel for something..."
Charlie quickly joined in the speculation, questioning Dexter: "Do you know something? You went up to the Diary Room twice, she's [Hazel] been up three times... you won't tell us what you're laughing about."
An unimpressed Gina concluded: "This is making me feel so immature, all this giggling."
Big Brother airs nightly on Channel 5.