I'm sorry that your shoe IS missing. My dog HAS taken it into the garden. I'm sorry that your shoe WAS missing. My dog HAD taken it into the garden Compare the two and learn!

That's the past perfect form. We use this when thing A happens before thing B, but they are both in the past. Example: "I had finished watching TV when the phone rang" (This happened last night/last week/last month, etc.) The present perfect uses "has/have" to show that something started in the past and continues until now (e.g., "I have lived in Shanghai for six years"); or to tell news (e.g., "There has been an earthquake in Mexico"). Saying that the dog "has taken" something into the garden means that you are announcing this news for the first time.

Jeremy, Either way could make sense, depending on the context. The man was looking for it. My dog had taken it into the garden before he started looking for it. The man is looking for it. My dog has taken it into the garden at some time in the recent past. It is in the garden now. I was able to find the reference on the net. What had happened to the writer's bag? After I had had lunch at the village pub, I looked for my bag. I had left it on a chair beside the door and it wasn't there! As I was looking for it the landlord came in. "Did you have a good meal?" he asked. "Yes, thank you," I answered, "but I can't pay for the meal. I haven't got my bag." The landlord smiled and immediately went out. In a few minutes he returned with my bag and gave it back to me. "I'm very sorry," he said. "My dog had taken it into the garden. He often does this." You can see from the context that the past perfect is correct. The man was looking for the bag. The dog had already taken it into the garden. The landlord found the bag, apologized, and explained why the man had not been able to find the bag: Because the dog had taken it into the garden (before the customer started looking for it, of course.) This dog has a very bad habit. If you used the present perfect tense you would change the story. What had happened to the writer's bag? After I had had lunch at the village pub, I looked for my bag. I had left it on a chair beside the door and it wasn't there! As I was looking for it the landlord came in. "Did you have a good meal?" he asked. "Yes, thank you," I answered, "but I can't pay for the meal. I haven't got my bag." The landlord smiled . "I'm very sorry," he said. "My dog has taken it into the garden. He often does this." He immediately went out. In a few minutes he returned with my bag and gave it back to me. This is a bad dog. .

Yes, it's past perfect. Usually, you need another (later) past event which it refers to, but it is possible to use past perfect by itself. The effect is that another past event is implied instead of being openly declared. Note that the speaker said "I'm very sorry"? :) Obviously something happened in the past to provoke that apology, so "My dog had taken it into the garden" refers to the event which caused the reason for the apology. If you use "has", it means the thing that the dog took into the garden is still there.

Pay attention to that "had left it" in the first line of your story. And my advice is, don't be too serious about tenses, otherwise you can always find tense mistakes in a story and unavoidable mistakes.