Henry wants to fool Mum as to his location with Echo-Bot but he needs to find the Remote Control.

Grandpa has left you a clue inside of Echo-Bot. Explore that further.

Grandpa's Watch fell out of Echo-Bot when you entered the Vox Recorder. It may not be clear why, initially, but he's left this for you to find.

Find it here.

Examine it carefully. When you go to the inventory, select the eye and then the Watch. The Watch is categorised under the eye instead of the hand, which you have likely been using to view the inventory so far.

Have you seen the symbols on Grandpa's Watch somewhere?

The symbols relate to the keypad next to the door to Grandpa's Study.

Enter these symbols into the keypad next to Grandpa's Study door.

Don't forget that you can use the space bar to display all of the hotspots for any given scene. If you click on every single one, you'll find it.