In Biggles in the Blue, Susannah Shaw was the widow of a Inagua islander who had been employed by the government to look after the flamingo nests on Inagua. They lived in a small hut in an otherwise derelict village near the lake on Inagua where the flamingoes nested. When her husband died, Shaw had found herself destitute and began stealing the flamingo eggs to sell in Matthewtown, the main settlement on Inagua. During this time, she observed a man coming from the sea carrying a box which he then buried in the floor of a hut which her husband had built by the shore of the flamingo lake. Over a period of time, the man continued to visit the hut but then he stopped coming. Shaw waited long enough to conclude that he would no longer come and then went to the hut to fetch the box which she thought must contain treasure.
When Biggles met Shaw, she was trying to break the box open with her axe. Susannah didn't know it, but the man with the box was Werner Wolff, a Nazi war criminal and the box contained not treasure but blueprints of Nazi secret weapons that were under development at the end of the Second World War. When Biggles explained the background to her, she surrendered the box to him readily. Biggles gave her some money and promised to recommend that the government appoint her as guardian of the flamingoes at the same salary as her husband. However he made her promise not to steal any more flamingo eggs.
Shaw's action of removing the box from the hut had actually served a useful purpose. Earlier on, both Biggles and von Stalhein team had been heading for the hut hoping to be the first ot get hold of the box. A stand off developed at the hut which might have turned violent but this was defused when von Stalhein discovered that the hut was empty. It was coming away from this confrontation that Biggles met Susannah Shaw trying to break open the box and so was able to take possession of it easily. Later, Ginger and Bertie, while carrying the box to the location where Biggles would land to pick them up, found themselves cornered by a hostile submarine. Biggles ordered them to sink the box in deep water so that neither side would get hold of its contents. The box sank easily, thanks to the damage Shaw had done to the box.
At the conclusion of the book, Biggles kept his word and submitted his recommendation to the governor of the Bahamas which resulted in Shaw being appointed to the post her husband used to hold.