Approach door of judge's residence and ring a bell: what ensures you, that there is no inside.
Go up the street and turn to gate leading on a house's backs. Open it and go in.
Get interested in a closed kitchen window: Holmes decides that he need a thin pin to open it.
Watson will find it. Return on the street and talk to a florist, standing o the left from entrance to Beckett's house. Talk to her - she turns out to be a Lucy, who Watson knows already. She'll give him a hairpin.
Return to Holmes and give him a hairpin. As Sherlock, approach a window and use it.
The riddle appears - you have to bend a pin properly, as it's shown above. So click:
- first part of pin 1x up;
- second 2x down;
- first again 1x up;
- second 1x down;
- third 1x up;
- fourth 2x down;
- and then "Confirm".
You get to a kitchen: through door by window go to the classroom of lady Beckett.