📖 The quiet case — order, time and money
The Vanished Volume is the library case, and it is the one that most resembles the real world. Somebody retyped a catalog card and walked out with the Grand Library's most treasured book, and catching them means doing the unglamorous things librarians actually do: reading numbers precisely, putting things in the right order, reckoning with clocks and reckoning with money. It carries the standards that children most often meet as isolated worksheet topics — telling the time, counting change, rounding, place value — and gives them somewhere to belong. It's also the brightest of the six to look at: parchment and warm wood rather than neon, which suits children who find the space and heist themes a bit loud.
The Grand Library's most treasured book vanished when someone secretly retyped its catalog card. Crack the card catalog, reshelve the scrambled stacks, beat the due-date desk and check the receipts to unmask the book-napper.
Each round is a different interactive mechanic — not the same question in a new coat. Crack all four to unmask the culprit.
The same story, re-levelled for each grade against its own Common Core standards. Pick your child's grade:
| Grade | Skill focus | Standards | XP | |
|---|---|---|---|---|
| Kindergarten | Numbers to 20: count, order & stack | K.CC.A.3 K.CC.C.7 K.OA.A.2 K.CC.B.5 | ⚡ 100 XP | Launch → |
| Grade 1 | Two-digit order, time to the half-hour | 1.NBT.A.1 1.NBT.B.3 1.MD.B.3 1.OA.A.1 | ⚡ 110 XP | Launch → |
| Grade 2 | Time, money & place value | 2.NBT.A.3 2.NBT.A.4 2.MD.C.7 2.MD.C.8 | ⚡ 130 XP | Launch → |
| Grade 3 | Rounding, fractions & elapsed time | 3.NBT.A.1 3.NF.A.3.d 3.MD.A.1 3.OA.A.3 | ⚡ 140 XP | Launch → |
| Grade 4 | Decimals, elapsed time & change | 4.NBT.A.2 4.NF.C.7 4.MD.A.2 | ⚡ 150 XP | Launch → |
| Grade 5 | Dewey decimals & conversions | 5.NBT.A.3 5.MD.A.1 5.NBT.B.7 | ⚡ 160 XP | Launch → |
Earns the 🏅 Book Sleuth badge.
Across K–5, The Vanished Volume covers these 22 standards. Mastery is tracked per standard for each agent. Official Common Core wording:
| 1.MD.B.3 | Tell and write time in hours and half-hours using analog and digital clocks. |
|---|---|
| 1.NBT.A.1 | Count to 120, starting at any number less than 120. In this range, read and write numerals and represent a number of objects with a written numeral. |
| 1.NBT.B.3 | Compare two two-digit numbers based on meanings of the tens and ones digits, recording the results of comparisons with the symbols >, =, and <. |
| 1.OA.A.1 | Use addition and subtraction within 20 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem. |
| 2.MD.C.7 | Tell and write time from analog and digital clocks to the nearest five minutes, using a.m. and p.m. |
| 2.MD.C.8 | Solve word problems involving dollar bills, quarters, dimes, nickels, and pennies, using $ and ¢ symbols appropriately. |
| 2.NBT.A.3 | Read and write numbers to 1000 using base-ten numerals, number names, and expanded form. |
| 2.NBT.A.4 | Compare two three-digit numbers based on meanings of the hundreds, tens, and ones digits, using >, =, and < symbols to record the results of comparisons. |
| 3.MD.A.1 | Tell and write time to the nearest minute and measure time intervals in minutes. Solve word problems involving addition and subtraction of time intervals in minutes, e.g., by representing the problem on a number line diagram. |
| 3.NBT.A.1 | Use place value understanding to round whole numbers to the nearest 10 or 100. |
| 3.NF.A.3.d | Compare two fractions with the same numerator or the same denominator by reasoning about their size. Recognize that comparisons are valid only when the two fractions refer to the same whole. Record the results of comparisons with the symbols >, =, or <, and justify the conclusions, e.g., by using a visual fraction model. |
| 3.OA.A.3 | Use multiplication and division within 100 to solve word problems in situations involving equal groups, arrays, and measurement quantities, e.g., by using drawings and equations with a symbol for the unknown number to represent the problem. |
| 4.MD.A.2 | Use the four operations to solve word problems involving distances, intervals of time, liquid volumes, masses of objects, and money, including problems involving simple fractions or decimals, and problems that require expressing measurements given in a larger unit in terms of a smaller unit. Represent measurement quantities using diagrams such as number line diagrams that feature a measurement scale. |
| 4.NBT.A.2 | Read and write multi-digit whole numbers using base-ten numerals, number names, and expanded form. Compare two multi-digit numbers based on meanings of the digits in each place, using >, =, and < symbols to record the results of comparisons. |
| 4.NF.C.7 | Compare two decimals to hundredths by reasoning about their size. Recognize that comparisons are valid only when the two decimals refer to the same whole. Record the results of comparisons with the symbols >, =, or <, and justify the conclusions, e.g., by using a visual model. |
| 5.MD.A.1 | Convert among different-sized standard measurement units within a given measurement system (e.g., convert 5 cm to 0.05 m), and use these conversions in solving multi-step, real world problems. |
| 5.NBT.A.3 | Read, write, and compare decimals to thousandths. |
| 5.NBT.B.7 | Add, subtract, multiply, and divide decimals to hundredths, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used. |
| K.CC.A.3 | Write numbers from 0 to 20. Represent a number of objects with a written numeral 0-20 (with 0 representing a count of no objects). |
| K.CC.B.5 | Count to answer "how many?" questions about as many as 20 things arranged in a line, a rectangular array, or a circle, or as many as 10 things in a scattered configuration; given a number from 1—20, count out that many objects. |
| K.CC.C.7 | Compare two numbers between 1 and 10 presented as written numerals. |
| K.OA.A.2 | Solve addition and subtraction word problems, and add and subtract within 10, e.g., by using objects or drawings to represent the problem. |
The 'measurement and data' strand more than any other case — time, money, rounding and place value — plus decimals at the upper grades. The full list, with official Common Core wording, is on this page.
This is the case for them. It's the calmest of the six in both look and pace — warm parchment colours, no timers, no alarms.
Yes — it appears from Grade 1 (hours and half-hours) through Grade 3 (to the minute, plus elapsed time). It's one of the most commonly under-practised parts of the curriculum.