While being outside, pay an attention on a tool panel opposite to the open door.
Then go right, to the rail tracks.
Go along the path on right from the track, until you get under a closed gate. Click it.
Try to get on the other side via track on the left. Unfortunately, it's slipped.
Point at levers (on the left from gate) which moves a platform. Transport a dog on the other side of broken track.
Go to the rail car full of crates. Release a brake. Platform will rolls to the broken part of track and Holmes will be able to join Toby.