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B1 English • Unit: Mysteries & Legends

🕵️ DETECTIVE THEORIES: A Mystery Deduction Game

Solve mysteries using these modal verbs: must be, might be, could be, and can't be.

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1. Rules of the Game

Students playing the mystery card game in class

👨‍🏫

For the Teacher

1 Make groups of 3 or 4 students. Choose one Scorekeeper for each group.
2 Give each group one Mystery Card face down. Explain the rules.
3 Tell teams to read Clues one by one. They must say one theory for each clue.
4 Tell students to swap cards at Step 4. Watch the 25-minute timer.
5 Listen to their English and check scores. Use the Teacher Key to check answers.

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For the Students

1 Goal: Work as detectives. Solve the mystery using clues and good theories.
2 Read Clue 1 together. Talk about it. Say one theory using must, might, could, or can't + be.
3 Do this again for Clue 2 and Clue 3. Your theories will change with new clues.
4 In Step 4, swap your card with another team. Try to solve their mystery.
5 Earn points for good grammar and Unit words. Then vote for the best theory.

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2. Timed Plan (25 Minutes Total)

Step 1 3m

Team Setup

Make groups and choose a scorekeeper. Give out mystery cards face down.

Kickoff

Step 2 7m

Clues 1 & 2

Read the first two clues. Make your first theories with modal verbs.

First Deductions

Step 3 6m

Clue 3 Reveal

Read the last clue. Change your ideas and choose your best team theory.

Finalizing Theory

Step 4 5m

Card Swap!

Swap mystery cards with another group. Try to solve their mystery.

Peer Exchange

Step 5 4m

Vote & Wrap-up

Count your points. Share your favorite theories and vote for the winner.

Scoring & Winner

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3. Mystery Cards (Printable Case Files)

An atmospheric, dimly lit room with an old wooden desk, a magnifying glass, and mysterious papers scattered about. High-

🔍 CASE FILE #01

Old house with a lit window

A light in the old house

❓ 1 Nobody has lived in the house for ten years.

❓ 2 There is a light in an upstairs window.

❓ 3 The front door is closed.

🔍 CASE FILE #02

Parcel outside a door

A strange parcel

❓ 1 A parcel is outside your door.

❓ 2 It has no name or address.

❓ 3 It is very light and makes a small noise.

🔍 CASE FILE #03

Empty classroom with ringing phone

The empty classroom

❓ 1 The classroom door is open.

❓ 2 All the chairs are on the desks.

❓ 3 A phone is ringing under a desk.

🔍 CASE FILE #04

Footprints stopping at the water

Footprints on the beach

❓ 1 There are big footprints on the beach.

❓ 2 They stop at the water.

❓ 3 The tide is coming in.

🔍 CASE FILE #05

Neighbor's house lit up at night

A new neighbour

❓ 1 A new neighbour has moved in next door.

❓ 2 You never see them in the day.

❓ 3 Their lights are on all night.

🔍 CASE FILE #06

Silent smartphone on a table

The silent phone

❓ 1 A friend usually messages you every day.

❓ 2 You have had no message for three days.

❓ 3 Their social media page is quiet too.

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4. Detective Scoring System

+1 Point

Correct sentence

Makes a correct sentence using:

must / might / could / can't + be

Recorded by team scorekeeper

+1 Point

Unit words

Uses any of the 10 target unit words:

mystery legend ghost treasure clue solve theory ancient strange hidden

Max 1 point per sentence

+3 Points

Class Best Vote

Awarded at the end of the game. The class votes for the best and most creative theory.

Voted by the whole class!

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5. Detective Sentence Starters

A clean, conceptual iconographic style showing three speech bubbles with different shades indicating certainty: one stro

1 Sure

"It must be a ghost because..."

2 Maybe

"This clue might be about a hidden treasure..."

3 Not possible

"It can't be a legend, because ..."

4 Maybe

"My theory is that it could be a strange animal..."

5 Sure

"It can't be a real mystery, because there must be a simple answer..."

6 Maybe

"It could be a clue, because ..."

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6. Teacher key and mistakes to listen for

💡 Teacher key: Sample Detective Theories

Listen for these sentences when you walk around the room:

Card 1: Old House 🏚️

"It can't be empty. Someone must be inside."
"It might be a ghost or someone hiding."

Card 2: Strange Parcel 📦

"It could be a strange pet or a clock."
"It can't be a heavy book. It might be a toy."

Card 3: Empty Classroom 🏫

"A student might be looking for their lost phone."
"It can't be class time. The cleaner might be nearby."

Card 4: Footprints 👣

"It might be an ancient sea creature."
"It can't be a car. Someone could be swimming."

Card 5: New Neighbour 🏠

"They might be a night-shift worker."
"They might be a vampire. They might have strange habits!"

Card 6: Silent Phone 📱

"They could be on a trip with no phone signal."
"Their phone could be broken or lost."

⚠️ Mistakes to Listen For

"It mustn't be a ghost"

➔ Fix: "It can't be a ghost"

Use can't be for things that are impossible. Do not use mustn't.

"It must to be a parcel"

➔ Fix: "It must be a parcel"

Never add 'to' after modal verbs.

"It could a hidden clue"

➔ Fix: "It could be a hidden clue"

Do not forget the verb be after the modal.

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7. Game variations

Level 1 🌱

Easy Mode

Write the vocabulary and modal verbs on the board to help students.

Help on the board

Level 2 ⚖️

Standard Mode

Normal game: every student must say one different theory before the group agrees.

Everybody speaks

Level 3 🔥

Challenge Mode

Each sentence must use one modal verb AND at least two Unit words.

More unit words

Fast ⚡

Plot Twist Clue

Write a 4th clue for your card. Give it to another group to solve.

Make a new clue

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8. Closing questions

Difficulty & Key Clues

Which mystery was the hardest to solve? Which clue helped your group the most?

Discussion point 🔍 Analysis

Creativity Spotlight

What was the most creative or strange theory you heard today?

Peer review ✨ Imagination

Grammar Reflection

When we are 100% sure something is impossible, which modal verb do we use?

🎯 Rule check

Class activity: Detective Theories (Deduction Game)