He says "The drive into the unknown", so unless he is playing with us it is the going part.Where is the bag that Aiden had?
Are they going someplace or are thsy comming back from somepalce?
If the bag had the suit inside we can assume it has been thrown away (possibly in the proper bin for ecological reasons).
And again, even for Aiden driving to Sophia with the shopping bag was not so easy and safe, imo
Also concerning the "unknown", it's true that it would be weird and unrealistic for Sophia to accept to go with him without any other information (unknown). So much for the realism. Unless, the phrase is just for us as a teaser, the unknown for us, while Sophia got a minimum of information about the task or where they are headed, to take an "informed decision"
As usual it depends on the context, an image says a thousands words but the dialogues can make a hell of difference!