These are my thoughts and questions.
Well done everyone who guessed Alice wads in the boot!
Lucy could be Alice's baby. The video of Sophie shortly before her abduction made her look pregnant - that could be the pregnancy that was spotted when she returned as Alice. We still don't know what went on between Julien and Sophie's dad.
Why did Sophie return as Alice? Maybe because they were held in Germany near site of Alice's abduction, the return of Sophie nearby would have established a clear link between the 2 abductions, and that might have yielded more clues (e.g. looking at who was in Germany and France at the relevant times for the 2 abductions) .so it was better that everyone thought she was Alice. Also, disposing of Lena and giving closure to the Websters would have been bonuses in Gettrick's mind.
But then why did Sophie say her name in ambulance? That was a definite mistake from Gettrick's point of view, I bet he was very angry about that.
When did Stone and Reed find out about the abductions? I think that was in 2014, not before. Sophie, or one of the others, got ill and Gettrick decide to enlist his help, blackmailing him with what happened in Iraq and his knowledge about Reed's visits to prostitutes. Then G decided to kill Reed, because he couldn't rely on Reed's silence.
Gettrick also needed Stone's help to mess with evidence and to keep the German civilian police off the case.
Gettrick was taking a risk with telling Stone and Reed but probably felt he had no choice, Stone had been the one who set fire to the house, and Reed was implicated by association. Both had careers they would not want to lose.
Why was Aldi shacked up with a butcher in the town she had previously been stationed? I'm sure in an earlier episode she said she met him online, but it must have been deliberate on her part to seek out a partner in Eckhaiusen. Otherwise its a massive coincidence. Or did I misunderstand, and she met butcher while she was stationed there?