Well, it has been quite a long time since I finished the first four épisodes of the Blackwell series and my mind is not so fresh about the whereabouts of the protagonists, for example : who was the ghost lady in red, what was the secret organisation behind some shady business in the last episode, have the powers of the heroine evolved and so on... I think it could also be useful for other people who are also in my case (no time to replay the 4 episodes).

For a start, here are two well written walkthroughs of the first and second game of the series.
They don't tell the single steps, but the story that's going on, so they're readable as summaries.

The Blackwell Legacy (2006)
http://gamingafter40.blogspot.de/2012/02/adventure-of-week-blackwell-legacy-2006.html

Blackwell Unbound (2007)
http://www.gamingafter40.blogspot.de/2012/08/adventure-of-week-blackwell-unbound-2007.html

And here are short summaries of part 3 and 4 on Wikipedia. Not very detailed but better than the average walkthrough.
Blackwell Convergence (2009)
http://en.wikipedia.org/wiki/The_Blackwell_Series#Blackwell_Convergence

Blackwell Deception (2001)
http://en.wikipedia.org/wiki/The_Blackwell_Series#Blackwell_Deception

You should do a replay, they very short games.