We Honestly Can Look After Your Dog by Lauren Child

Lola loves dogs. So when Charlie takes Lola and her friend Lotta to the park with his friend Marv and Marv's dog Sizzles, Lola is thrilled. Marv lets her and Lotta look after Sizzles on the promise that they don't let him off the lead. But Lola and Lotta are so excited that they let Sizzles go and then have a search for him all round the park.