Sherlock Season 4: 18 Easter Eggs & References From 'The Lying Detective'
7. Irene's Text Alert Noise
Again, casual viewers might have been surprised when Sherlock's phone emitted an erotic moan when he got a text from Irene Adler.
Back in 2012's A Scandal in Belgravia, Irene stole Sherlock's phone and permanently reset her personal text alert noise. It bought a red-faced Sherlock a lot of embarrassment in that episode, but we haven't heard of Irene texting him since then.
Rumours have persisted that Irene would make an appearance in this fourth season. Is that all we should expect of her or will she be back next episode?