Final answer:
Alfred doesn't warn Major and James about the burglar alarm because he is locked out and unable to communicate with them.
Step-by-step explanation:
In the given text, Alfred does not warn Major and James about the burglar alarm because he can't get to them due to locked doors and being unable to communicate with them. The passage states that Claire has the key to the outer door and is locked in, while Alfred is locked out without the key. Additionally, when Alfred tries to get their attention, they don't hear him. Therefore, Alfred's inability to reach Major and James and communicate with them prevents him from warning them about the burglar alarm.