The Missing series two led us through a thrilling, challenging case as Julien Baptiste attempted to discover what really happened to missing girl Alice Webster.
But, with all our attention focussed on trying to track down Adam Gettrick, it was easy to miss the little details from writers Harry and Jack Williams.
More: The Missing series finale review: one stunning series, one final cliffhanger
Case in point, did you spot the nice reference back to The Missing series one in tonight's series finale?
Julien Baptiste, Sam and Gemma Webster were searching Gettrick's house for clues that would reveal where he had disappeared to. Gemma found a bundle of Swiss francs that Gettrick had left behind.
With Julien spotting the picture of the mysterious hut on the wall, he decided to call an old friend for a favour.
He rang his "friend at Interpol" to ask whether he could help track down Gettrick in Switzerland.
The name of the old friend? Mark Walsh. The same Mark Walsh who featured in series one.
The detective was the British liaison officer during the investigation into the disappearance of Oliver Hughes. He eventually falls in love with Emily – Oliver's mother. The last we see of Mark is him marrying Emily, and Emily's ex-husband Tony Hughes looking awkward at the ceremony.
Did you spot the callback during the series two finale? And how many other little references have we missed along the way?
The Missing series 2 finale recap: is this the end for Julien Baptiste?