First Paragraph Tension

Take a look at these exciting first paragraphs from Maple children. On the last day of half term the children were challenged to write a story about three random elements (that were quite literally picked from a hat!). Identical twins, a secret diary and a scream all had to be included somewhere in their writing. Excitedly, children planned tales of kidnappers, escapees and long lost secrets. 

How have they successfully built suspense in these opening paragraphs?